MKSI MKS Instruments Inc

PRELIMINARY PROXY STATEMENT SUBJECT TO COMPLETION

MKS INSTRUMENTS, INC.

2 Tech Drive, Suite 201

Andover, Massachusetts 01810

April  , 2025

Dear Shareholder:

You are cordially invited to attend the 2025 Annual Meeting of Shareholders of MKS Instruments, Inc. to be held on Monday, May 12, 2025 at 10:00 a.m., Eastern Time, at our headquarters at 2 Tech Drive, Suite 201, Andover, Massachusetts 01810.

The attached notice of Annual Meeting and proxy statement describe the business to be transacted at the Annual Meeting and provide additional information about us that you should know when voting your shares. The principal business at the Annual Meeting will be (i) the election of two Class II Directors, each for a three-year term, (ii) the approval of an amendment to our Restated Articles of Organization, as amended, to lower the voting requirement for approval of certain matters from a supermajority to a simple majority voting standard, (iii) the approval of an amendment to our Second Amended and Restated By-Laws to lower the voting requirement for approval of an amendment to our By-Laws from a supermajority to a simple majority voting standard, (iv) the approval of an amendment to our Restated Articles of Organization, as amended, to change our name to MKS Inc., (v) the approval, on an advisory basis, of executive compensation, and (vi) the ratification of the selection of PricewaterhouseCoopers LLP as our independent registered public accounting firm for the year ending December 31, 2025.

Whether or not you plan to attend the Annual Meeting, please carefully review the attached proxy materials and take the time to cast your vote.

On behalf of MKS, I would like to express our appreciation for your continued interest in our Company.

MKS INSTRUMENTS, INC.

2 Tech Drive, Suite 201

Andover, Massachusetts 01810

NOTICE OF 2025 ANNUAL MEETING OF SHAREHOLDERS

TO BE HELD ON MONDAY, MAY 12, 2025 at 10:00 A.M. EASTERN TIME

To our Shareholders:

The 2025 Annual Meeting of Shareholders of MKS INSTRUMENTS, INC., a Massachusetts corporation, will be held on Monday, May 12, 2025 at 10:00 a.m., Eastern Time, at our headquarters at 2 Tech Drive, Suite 201, Andover, Massachusetts 01810, for the following purposes:

The shareholders will also act on any other business as may properly come before the meeting.

We provide access to our proxy materials over the Internet under the U.S. Securities and Exchange Commission’s “notice and access” rules. As a result, we mail to our shareholders a Notice of Internet Availability of Proxy Materials, which we refer to as the Notice. We are mailing the Notice on or about April  , 2025, and it contains instructions on how to access the proxy statement and our Annual Report for the fiscal year ended December 31, 2024, which we refer to as the 2024 Annual Report, over the Internet. The Notice also contains instructions on how our shareholders can receive a paper copy of our proxy materials, including this proxy statement, our 2024 Annual Report, and a form of proxy card or voting instruction card. All shareholders who do not receive the Notice, including shareholders who have previously requested to receive paper copies of proxy materials, will receive a paper copy of the proxy materials by mail unless they have previously requested delivery of proxy materials electronically.

The Board of Directors has fixed the close of business on March 4, 2025 as the record date for the determination of shareholders entitled to notice of, and to vote at, the Annual Meeting and any adjournment or postponement thereof. Your vote is important no matter how many shares you own. Whether or not you expect to attend the meeting, we urge you to vote your shares.

If you are a shareholder of record, you may vote by using the Internet or calling the toll-free telephone number as described in the instructions included in your Notice, or, if you received a paper copy of the proxy materials, by completing, signing, dating, and returning your proxy card or voting instruction card. If you are a beneficial shareholder (meaning the shares you own are held in “street name” by a bank, broker, or other nominee), you may vote by following the instructions your broker, bank, or other nominee provides to you. Your prompt response is necessary to ensure that your shares are represented at the meeting. You can change your vote and revoke your proxy any time before the polls close at the meeting by following the procedures described in the accompanying proxy statement.

Andover, Massachusetts

April  , 2025

TABLE OF CONTENTS

i

ii

MKS INSTRUMENTS, INC.

2 Tech Drive, Suite 201

Andover, Massachusetts 01810

PROXY STATEMENT

This proxy statement is furnished in connection with the solicitation of proxies by the Board of Directors of MKS Instruments, Inc., a Massachusetts corporation, for use at the 2025 Annual Meeting of Shareholders to be held on Monday, May 12, 2025 at 10:00 a.m., Eastern Time, at our headquarters at 2 Tech Drive, Suite 201, Andover, Massachusetts 01810, and at any adjournment or postponement thereof, which we refer to as the 2025 Annual Meeting. References in this proxy statement to “we,” “us,” the “Company,” or “MKS” refer to MKS Instruments, Inc. and its consolidated subsidiaries.

All proxies will be voted in accordance with the applicable shareholder’s instructions. If no choice is specified in the proxy, the shares will be voted in accordance with the recommendations of our Board of Directors. The Board of Directors recommends that you vote FOR each director nominee and FOR each of Proposals 2, 3, 4, 5, and 6. Any proxy may be revoked by a shareholder at any time before its exercise by delivery of written revocation to the Secretary of MKS or by voting during the 2025 Annual Meeting. Attendance at the 2025 Annual Meeting will not in itself be deemed to revoke a proxy.

We provide access to our proxy materials over the Internet under the “notice and access” rules of the U.S. Securities and Exchange Commission, which we refer to as the SEC. As a result, we mail to our shareholders a Notice of Internet Availability of Proxy Materials, which we refer to as the Notice. We are mailing the Notice on or about April , 2025. The Notice contains instructions on how to access the proxy statement and our Annual Report for the fiscal year ended December 31, 2024, which we refer to as the 2024 Annual Report, over the Internet. The Notice also contains instructions on how our shareholders can receive a paper copy of our proxy materials, including this proxy statement, our 2024 Annual Report, and a form of proxy card or voting instruction card. All shareholders who do not receive the Notice, including shareholders who have previously requested to receive paper copies of proxy materials, will receive a paper copy of the proxy materials by mail unless they have previously requested delivery of proxy materials electronically.

Important notice regarding the availability of proxy materials for the 2025 Annual Meeting to be held on May 12, 2025: This proxy statement and the 2024 Annual Report are available for viewing, printing, and downloading free of charge at investor.mks.com/annual-meeting-materials.

VOTING OF SECURITIES AND VOTES REQUIRED

At the close of business on March 4, 2025, the record date for the determination of shareholders entitled to notice of, and to vote at, the 2025 Annual Meeting, there were issued and outstanding and entitled to vote 67,447,167 shares of our common stock, no par value per share, which we refer to as our Common Stock. Each outstanding share entitles the record holder to one vote on each matter submitted at the 2025 Annual Meeting.

In order to transact business at the 2025 Annual Meeting, we must have a quorum. Under our Second Amended and Restated By-Laws, or our By-Laws, the holders of a majority of the shares of Common Stock issued and outstanding and entitled to vote at the 2025 Annual Meeting shall constitute a quorum for the transaction of business at the 2025 Annual Meeting. Shares of Common Stock held by shareholders present at the 2025 Annual Meeting or represented by proxy (including “broker non-votes” and shares that abstain or do not vote with respect to a particular proposal to be voted upon) will be counted for purposes of determining whether a quorum exists at the 2025 Annual Meeting. If a quorum is not present, the meeting will be adjourned until a quorum is obtained.

For the election of directors (Proposal 1), you may vote “For” or “Withhold” for each director nominee. The affirmative vote of the holders of a plurality of the votes cast on the matter is required for the election of directors; provided, however, any director nominee who receives a greater number of withhold votes than affirmative votes, which we refer to as a Majority Withheld Vote, in an uncontested election must offer to tender to the Board of Directors his or her resignation promptly following the certification of election results. The Board of Directors must accept or reject a resignation within 90 days following the certification of election results and publicly disclose its decision. Accordingly, the nominees who receive the highest number of votes of the shares present, in person or by proxy, and entitled to vote shall be elected to the available Class II Director positions, and in the event any nominee receives a Majority Withheld Vote, the resignation policy will apply as summarized here and as set forth

in Section B.4 of our Corporate Governance Guidelines, which are posted on our website at www.mks.com/corporate-governance under Corporate Governance Documents.

For the amendment to our Restated Articles of Organization, as amended, or our Articles, to lower the voting requirement for approval of certain matters from a supermajority to a simple majority voting standard (Proposal 2), the amendment to our By-Laws to lower the voting requirement for approval of an amendment to our By-Laws from a supermajority to a simple majority voting standard (Proposal 3), the amendment to our Articles to change our name to MKS Inc. (Proposal 4), the advisory vote on executive compensation (Proposal 5), and the ratification of PricewaterhouseCoopers LLP (Proposal 6), you may vote “For,” “Against,” or “Abstain.” Because our Board of Directors has approved the amendments to our Articles as described in Proposals 2 and 4, each of Proposal 2 and Proposal 4 requires the affirmative vote of the holders of a majority of our outstanding shares entitled to vote on the matter. Proposal 3 requires the affirmative vote of the holders of two-thirds of our outstanding shares entitled to vote on the matter. Proposals 5 and 6 require the affirmative vote of the holders of a majority of the votes cast on the matter. Proposal 5 is a non-binding proposal.

Shares held by shareholders who abstain from voting as to a particular matter, and “broker non-votes,” which are shares held in “street name” by banks, brokers, or other nominees who indicate on their proxies that they do not have discretionary authority to vote such shares as to a particular matter, are not counted as votes with respect to any of the items to be voted on at the 2025 Annual Meeting. We expect that brokers will not have discretionary authority to vote on Proposals 1, 2, 3, and 5 and will have discretionary authority to vote on Proposals 4 and 6. Abstentions and broker non-votes, if any, will have no effect on Proposals 1, 5, and 6, and will have the effect of a vote against Proposals 2, 3, and 4. If the shares you own are held in street name by a bank, broker, or other nominee, then your bank, broker, or other nominee, as the record holder of your shares, is required to vote your shares according to your instructions. In order to vote your shares, you will need to follow the instructions your bank, broker, or other nominee provides to you.

For additional details about voting and attending the 2025 Annual Meeting, see “Voting and Meeting Information” below.

VOTING AND MEETING INFORMATION

The following sections provide additional details about voting and attending the 2025 Annual Meeting.

Voting Your Shares

If you are a shareholder of record, you may vote your shares in any of the following ways:

		Internet
		You may vote your shares in advance of the 2025 Annual Meeting via the Internet by accessing our online portal at www.proxyvote.com. Proxies submitted via the Internet must be received by 11:59 p.m. Eastern Time on May 11, 2025.
		Telephone
		You may vote your shares in advance of the 2025 Annual Meeting telephonically by calling 1-800-690-6903 and following the instructions on your proxy card. Proxies submitted by telephone must be received by 11:59 p.m. Eastern Time on May 11, 2025.
		Mail
		If you received a paper copy of the proxy materials, you may vote your shares in advance of the 2025 Annual Meeting by completing, signing, dating, and returning your proxy card or voting instruction card. Proxies submitted via mail must be received by May 11, 2025.
		In-Person at the 2025 Annual Meeting
		You may vote your shares during the 2025 Annual Meeting by (i) if you received a paper copy of the proxy materials, completing your proxy card or voting instruction card or (ii) if you did not receive a paper copy of the proxy materials, completing a ballot to be provided by the Company at the 2025 Annual Meeting. If you have previously submitted your proxy and you vote your shares in accordance with these instructions during the 2025 Annual Meeting, your previously submitted proxy will be revoked.

If you are a beneficial shareholder (meaning the shares you own are held in “street name” by a bank, broker, or other nominee), your bank, broker, or other nominee will provide a vote instruction form to you with this proxy statement, which you may use to direct how your shares will be voted. You must instruct your bank, broker, or other nominee how to vote with respect to the election of directors, the amendment to our Articles to lower the voting requirement for approval of certain matters from a supermajority to a simple majority voting standard, the amendment to our By-Laws to lower the voting requirement for approval of an amendment to our By-Laws from a supermajority to a simple majority voting standard, and the executive compensation advisory vote; your bank, broker, or other nominee cannot exercise its discretion to vote on these matters on your behalf. Many banks and brokers offer the option of voting over the Internet or by telephone, instructions for which would be provided by your bank or broker on your vote instruction form. You may only vote your shares in-person at the 2025 Annual Meeting if you obtain a proxy issued in your name from your bank, broker, or other nominee. For instructions on how to revoke or change your vote, you should contact your bank, broker, or other nominee.

Attending the 2025 Annual Meeting

Admission of shareholders of record and beneficial shareholders to the 2025 Annual Meeting will begin at 9:45 a.m. Eastern Time. Shareholders of record who wish to attend the meeting should be prepared to present photo identification and beneficial shareholders who wish to attend the meeting should be prepared to present photo identification and a letter from their bank, broker, or other nominee confirming beneficial ownership of shares of our Common Stock.

Proxy Materials

You can view and download our proxy materials and 2024 Annual Report at our online portal, available to shareholders at www.proxyvote.com.

Shareholder List

During the 2025 Annual Meeting, a complete list of our shareholders of record will be available for viewing by shareholders for any purpose germane to the 2025 Annual Meeting. Shareholders submitting any such request will be asked to provide the 16-digit control number found on their proxy card, voting instruction card, or Notice.

Whether or not you plan to attend the 2025 Annual Meeting, we urge you to vote your shares over the Internet or by telephone, or complete, sign, date, and return the proxy card in the accompanying postage-prepaid envelope if you received a printed proxy card. A prompt response will greatly facilitate arrangements for the 2025 Annual Meeting and your cooperation will be appreciated. Shareholders who attend the 2025 Annual Meeting may vote their shares at the 2025 Annual Meeting even if they have previously sent in their proxies.

PROPOSAL 1 – ELECTION OF DIRECTORS

Our Board of Directors is currently divided into three classes. The term of the Class II Directors expires at the 2025 Annual Meeting, the term of the Class III Directors expires at the 2026 Annual Meeting of Shareholders, or the 2026 Annual Meeting, and the term of the Class I Directors expires at the 2027 Annual Meeting of Shareholders. Pursuant to our By-Laws, our Board of Directors will be declassified over a three-year period beginning with the 2026 Annual Meeting, resulting in the Board being fully declassified (and all directors standing for annual elections) beginning with the 2028 Annual Meeting of Shareholders, or the 2028 Annual Meeting.

Our Board of Directors, upon the recommendation of our Nominating and Corporate Governance Committee, has nominated John T.C. Lee and Jacqueline F. Moloney to serve as Class II Directors for a term to expire at the 2028 Annual Meeting. Dr. Lee and Dr. Moloney currently serve as directors. Each nominee has consented to being named herein and, if elected, to serve as a director until his or her successor is duly elected and qualified.

Michelle M. Warner, who currently serves as a Class II Director, is not standing for re-election to the Board of Directors. The Board of Directors previously approved a decrease in the size of the Board of Directors effective immediately prior to the 2025 Annual Meeting, which eliminates the vacancy that would have existed at the 2025 Annual Meeting. Proxies cannot be voted for a greater number of persons than the number of nominees named in this proxy statement.

Shares represented by all proxies received by the Board of Directors and not so marked as to withhold authority to vote for an individual director will be voted (unless one or more nominees are unable or unwilling to serve) for the election of the nominees named below. The Board of Directors expects that each of the nominees named below will be available for election, but if either of them is not a candidate at the time the election occurs, it is intended that such proxies will be voted for the election of a substitute nominee to be designated by the Board of Directors.

THE BOARD OF DIRECTORS BELIEVES THAT APPROVAL OF THE ELECTION OF JOHN T.C. LEE AND JACQUELINE F. MOLONEY TO SERVE AS CLASS II DIRECTORS IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” BOTH NOMINEES.

DIRECTORS

Set forth below are the names and ages of each member of our Board of Directors (including those who are nominees for election as Class II Directors) and the positions and offices they hold with the Company. In addition, set forth below are biographies for each continuing director and director nominee, which include information about each individual’s specific experience, qualifications, attributes, or skills that led the Board of Directors to conclude that he or she should serve as a director of MKS. Information with respect to the number of shares of Common Stock beneficially owned by each individual, directly or indirectly, as of March 4, 2025, appears in this proxy statement under the heading “Security Ownership of Certain Beneficial Owners and Management.”

Name

Age

Position

Audit Committee

Compensation Committee

Nominating and Corporate Governance Committee

Class to Which Director Currently Belongs

Rajeev Batra

57

Director

I

Peter J. Cannone III

59

Director

III

Gerald G. Colella

68

Chair

I

Joseph B. Donahue

66

Director

III

Wissam G. Jabre

55

Director

III

John T.C. Lee*

62

Director, President and CEO

II

Jacqueline F. Moloney*

71

Lead Director

II

Elizabeth A. Mora

64

Director

I

Michelle M. Warner

58

Director

II

Chair

Member

Director Skills, Experience, and Background

MKS enables technologies that transform our world, delivering foundational technology solutions to leading edge semiconductor manufacturing, electronics and packaging, and specialty industrial applications. As discussed below under the heading “Corporate Governance – Director Candidates,” the Nominating and Corporate Governance Committee is responsible for evaluating the appropriate skills, experience, and background that MKS seeks in Board members in the context of our business and the existing composition of the Board of Directors. This evaluation includes numerous factors, such as integrity, business acumen, knowledge of our business and industries, effectiveness, experience, diligence, conflicts of interest, and the ability to act in the interests of all shareholders.

Listed below are the skills and experience that we consider important for our directors given our current business and organizational structure. The continuing directors’ and director nominees’ biographies above and the matrix below note each director’s and director nominee’s relevant experience, qualifications, and skills relative to this list.

Skills/Competencies

We serve a diverse base of customers across our semiconductor, electronics and packaging, and specialty industrial markets. Directors with education and experience in these end markets provide valuable perspectives on research and development, competing products and solutions, manufacturing and assembly, and market dynamics and trends.

Directors with experience in mergers and acquisitions and business development provide critical insights into developing and implementing strategies for growing our business, including skills in assessing and analyzing the “fit” of a proposed acquisition with our long-term strategy, valuing transactions, assessing integration plans, and overseeing integration activities for completed acquisitions into our existing operations.

Directors who have served in executive leadership positions have the experience and perspective to analyze, shape, and oversee the execution of important operational and policy issues.

Directors with board experience at other public companies understand the dynamics and operation of a corporate board, the relationship of a public company board to the chief executive officer and other executive officers, the legal and regulatory landscape in which public companies must operate, and how to oversee an ever-changing mix of strategic, operational, and compliance-related matters.

We are a global organization with manufacturing, research and development, and sales offices in over 35 countries. We sell our products to thousands of customers worldwide and a significant portion of our revenues are from sales to customers in international markets. Directors with international experience provide valuable business, regulatory, and cultural perspectives regarding many important aspects of our business.

Directors with experience analyzing and utilizing financial information to make informed business decisions assist the Board of Directors with advising on and overseeing our capital structure, our financing and investing activities as well as our financial reporting and internal controls.

Directors with experience in deploying innovative technologies provide critical insights into navigating our markets and industries, many of which are subject to rapid technological advancement that requires frequent innovation.

Directors with experience in risk management and governance assist the Board of Directors in fulfilling its oversight responsibilities regarding a range of regulatory, compliance, and risk management matters, including with respect to data privacy, cybersecurity, corporate governance, environmental and social matters.

Directors with marketing, brand management, and sales experience provide expertise and guidance as we seek to expand the markets in which we compete, grow sales, and strengthen our brands.

As we operate in many cyclical markets, with rapid demand changes, and have a broad footprint of international manufacturing operations, understanding of and experience with manufacturing and other operational processes are valuable assets to our Board of Directors.

Board Skills Matrix

The below matrix notes the experience, qualifications, and skills of each continuing director and director nominee relative to the skills and experience we consider important for our directors.

Directors

1

2

3

4

5

6

7

8

Skills/Competencies

• Domain Expertise

✓

✓

✓

✓

✓

• M&A/Business Development

✓

✓

✓

✓

✓

✓

✓

• Executive Leadership

✓

✓

✓

✓

✓

✓

✓

✓

• Experienced Public Company Director

✓

✓

✓

✓

✓

• Global Business

✓

✓

✓

✓

✓

✓

✓

• Financial Literacy

✓

✓

✓

✓

✓

✓

✓

✓

• Technology/Innovation

✓

✓

✓

✓

✓

✓

✓

✓

• Risk Management/Governance

✓

✓

✓

✓

✓

✓

✓

✓

• Marketing/Sales

✓

✓

✓

• Manufacturing/Operations

✓

✓

✓

✓

✓

Personal Demographics

• Tenure (years)

7

4

11

5

0

5

9

13

• Age

57

59

68

66

55

62

71

64

PROPOSAL 2 – AMENDMENT TO OUR RESTATED ARTICLES OF ORGANIZATION, AS AMENDED, TO LOWER VOTING REQUIREMENT FOR CERTAIN MATTERS FROM A SUPERMAJORITY TO A SIMPLE MAJORITY VOTING STANDARD

Under the Massachusetts Business Corporation Act, unless a corporation’s articles of organization provide for a different percentage, the affirmative vote of the holders of at least two-thirds of the outstanding shares of the corporation entitled to vote is required to amend the corporation’s articles of organization; approve a sale, lease, exchange, or otherwise dispose of all, or substantially all, of the corporation’s property, otherwise than in the usual and regular course of business; approve a plan of merger or share exchange; approve a plan of domestication of the corporation to a foreign jurisdiction; approve a plan of entity conversion to a domestic or foreign other entity; and approve a proposal to dissolve the corporation.

Currently, our Articles require the vote of at least sixty-six and two-thirds percent (66 2/3%) of the shares outstanding and entitled to vote thereon to authorize any amendment to our Articles; the sale, lease or exchange of all or substantially all of our property and assets, including our goodwill; and an agreement of merger or consolidation, unless our Board of Directors has previously approved these matters, in which case the affirmative vote of the holders of a majority of our outstanding shares is required. Therefore, if our Board of Directors has not previously approved these matters, the supermajority default under state law is applicable to shareholder votes on these matters.

After careful consideration and review, our Board of Directors has determined, subject to shareholder approval, to amend our Articles to provide that a simple majority voting standard always applies to shareholder votes on these matters.

While our Board of Directors believes that these actions should not be taken without the support of a substantial proportion of our shareholders, our Board of Directors is committed to corporate governance best practices and effectively addressing issues that matter to our shareholders. In determining to recommend this amendment, our Board of Directors considered the view of shareholders who believe these supermajority voting provisions may impede accountability to shareholders. Our Board of Directors also considered the view of shareholders who suggested that a lower shareholder voting threshold could increase shareholders’ ability to participate effectively in corporate governance. At the 2024 Annual Meeting of Shareholders, or the 2024 Annual Meeting, a significant majority of our shareholders approved a shareholder proposal asking us to implement a simple majority voting standard rather than the supermajority default under state law.

On February 10, 2025, the Board of Directors unanimously adopted resolutions approving and declaring the advisability of adopting an amendment to Article VI, Section 6C(d) of our Articles to effect this simple majority voting standard and recommended that shareholders approve the amendment by voting in favor of this proposal. The amendment provides that for any shareholder vote required in connection with:

the voting standard will be the affirmative vote of the holders of a simple majority of the outstanding shares of the Company entitled to vote on such matter.

If this proposal is approved by our shareholders, we intend to file Restated Articles of Organization with the Secretary of the Commonwealth of the Commonwealth of Massachusetts to effect this amendment promptly after the 2025 Annual Meeting.

The form of Restated Articles of Organization is attached as Appendix A to this Proxy Statement. In Appendix A, text stricken through indicates deletions and text that is underlined indicates additions to implement the proposed amendment. If this proposal is approved by our shareholders, the stricken text will not appear in the Restated Articles of Organization as filed with the Secretary of the Commonwealth of the Commonwealth of Massachusetts.

The above description of this amendment is qualified in its entirety by reference to the actual text of the Restated Articles of Organization set forth in Appendix A. The Restated Articles of Organization set forth in Appendix A also reflects the proposed change in name of the Company from “MKS Instruments, Inc.” to “MKS Inc.”, as described in Proposal 4 below. If Proposal 2 is approved by our shareholders but Proposal 4 is not approved by our shareholders, Article I of the Restated Articles of Organization will reflect the current name of the Company.

THE BOARD OF DIRECTORS BELIEVES THAT THE PROPOSAL TO AMEND OUR ARTICLES TO LOWER THE VOTING REQUIREMENT FOR CERTAIN MATTERS FROM A SUPERMAJORITY TO A SIMPLE MAJORITY VOTING STANDARD IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” THIS PROPOSAL.

PROPOSAL 3 – AMENDMENT TO OUR SECOND AMENDED AND RESTATED BY-LAWS TO LOWER VOTING REQUIREMENT FOR AN AMENDMENT TO OUR BY-LAWS FROM A SUPERMAJORITY TO A SIMPLE MAJORITY VOTING STANDARD

Our By-Laws currently require the affirmative vote of the holders of at least two-thirds of the outstanding shares of our Company entitled to vote to amend our By-Laws.

After careful consideration and review, our Board of Directors has determined, subject to shareholder approval, to amend our By-Laws to provide that a simple majority voting standard applies to shareholder votes on amendments to our By-Laws.

While our Board of Directors believes that an amendment to our By-Laws should not be made without the support of a substantial proportion of our shareholders, our Board of Directors is committed to corporate governance best practices and effectively addressing issues that matter to our shareholders. In determining to recommend this amendment, our Board of Directors considered the view of shareholders who believe this supermajority voting provision may impede accountability to shareholders. Our Board of Directors also considered the view of shareholders who suggested that a lower shareholder voting threshold could increase shareholders’ ability to participate effectively in corporate governance. At the 2024 Annual Meeting, a significant majority of our shareholders approved a shareholder proposal asking us to implement a simple majority voting standard.

On February 10, 2025, our Board of Directors unanimously adopted resolutions approving and declaring the advisability of adopting this amendment to our By-Laws and recommended that shareholders approve the amendment by voting in favor of this proposal. The amendment provides that for any shareholder vote required to amend our By-Laws, the voting standard will be the affirmative vote of the holders of a simple majority of the outstanding shares of the Company entitled to vote on such matter.

If this proposal is approved by our shareholders, this amendment will become effective immediately.

The proposed amendment to Article VIII of our By-Laws is set forth in Appendix B to this Proxy Statement, and the full text of our current By-Laws immediately follows the proposed amendment set forth therein. The above description of this amendment is qualified in its entirety by reference to the actual text of the proposed amendment set forth in Appendix B.

THE BOARD OF DIRECTORS BELIEVES THAT THE PROPOSAL TO AMEND OUR BY-LAWS TO LOWER THE VOTING REQUIREMENT FOR AN AMENDMENT TO OUR BY-LAWS FROM A SUPERMAJORITY TO A SIMPLE MAJORITY VOTING STANDARD IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” THIS PROPOSAL.

PROPOSAL 4 – AMENDMENT TO OUR RESTATED ARTICLES OF ORGANIZATION, AS AMENDED, TO CHANGE OUR NAME TO MKS INC.

Our Board of Directors has approved, and recommends that shareholders approve, an amendment to our Articles to change the name of the Company from “MKS Instruments, Inc.” to “MKS Inc.”.

We were founded in 1961 and initially offered industrial instruments to measure and control critical parameters in advanced manufacturing processes. Over the years, we have expanded our business far beyond these processes by organic growth through investment in research and development and entering new markets through strategic acquisitions, such as Newport Corporation, or Newport, in 2016, Electro Scientific Industries, Inc., or ESI, in 2019, and, most recently, Atotech Limited, or Atotech, in 2022. As a result, we have become a global provider of not only industrial instruments but also subsystems, systems, process control solutions, and specialty chemicals technology that improve process performance, optimize productivity, and enable unique innovations for many of the world’s leading technology and industrial companies. The Board of Directors believes that the breadth and scope of the Company’s activities is better reflected by the proposed name “MKS Inc.”. Accordingly, on February 10, 2025, our Board of Directors unanimously adopted resolutions approving and declaring the advisability of adopting this amendment to our Articles and recommended that shareholders approve the amendment by voting in favor of this proposal.

If this proposal is approved by our shareholders, Article I of our Articles will be amended to read as follows:

“The exact name of the corporation is: MKS Inc.”

If this proposal is approved by our shareholders, we intend to file Restated Articles of Organization with the Secretary of the Commonwealth of the Commonwealth of Massachusetts to effect this amendment promptly after the 2025 Annual Meeting.

The form of Restated Articles of Organization, which is attached as Appendix A to this Proxy Statement, also reflects the proposed amendment to lower the voting requirement for certain matters from a supermajority to a simple majority voting standard, as described in Proposal 2 above. If Proposal 4 is approved by our shareholders but Proposal 2 is not approved by our shareholders, we will only amend Article I of our Articles to reflect that our corporate name is “MKS Inc.”.

Changing our corporate name will not change our corporate structure or the names of any of our subsidiaries. Our common stock is listed for trading on The Nasdaq Global Select Market, or Nasdaq, under the symbol “MKSI.” Whether or not the name change becomes effective, our common stock will continue to be listed on Nasdaq under the symbol “MKSI.” If the name change becomes effective, the rights of shareholders holding certificated shares under currently outstanding stock certificates and the number of shares represented by those certificates will remain unchanged. The name change will not affect the validity or transferability of any outstanding stock certificates, nor will it be necessary for shareholders with certificated shares to surrender any stock certificates they currently hold as a result of the name change. After the name change, all new stock certificates we issue and all uncertificated shares held in direct registration accounts, including uncertificated shares currently held in direct registration accounts, will bear the name “MKS Inc.”.

THE BOARD OF DIRECTORS BELIEVES THAT THE PROPOSAL TO AMEND OUR ARTICLES TO CHANGE OUR NAME TO MKS INC. IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” THIS PROPOSAL.

PROPOSAL 5 – ADVISORY VOTE ON EXECUTIVE COMPENSATION

The Dodd-Frank Wall Street Reform and Consumer Protection Act of 2010, or the Dodd-Frank Act, enables our shareholders to vote to approve, on a non-binding, advisory basis, the compensation of our Named Executive Officers as disclosed in this proxy statement under the heading “Executive Compensation,” including “Compensation Discussion and Analysis,” the tabular disclosure regarding such compensation, and the accompanying narrative disclosure. This vote is not intended to address any specific item of compensation but rather the overall compensation of our Named Executive Officers and the philosophy, policies, and practices of executive compensation described in this proxy statement. The advisory vote is not a vote on our compensation practices for non-executive employees or our Board of Directors. The Dodd-Frank Act requires the Company to hold the advisory vote on executive compensation at least once every three years, but we have elected to submit the advisory vote to shareholders annually.

As described in detail under the heading “Executive Compensation — Compensation Discussion and Analysis,” our executive compensation program is designed to attract, motivate, and retain our executive officers, who are critical to our success. Under this program, our executive officers are rewarded for the achievement of specific short-term and long-term goals. Please see the “Compensation Discussion and Analysis” for additional details about our executive compensation program and philosophy, including information about the compensation of our Named Executive Officers.

The Compensation Committee continually reviews the compensation program for our executive officers to ensure it achieves the desired goals of aligning our executive compensation structure with our shareholders’ interests and current market practices. At the 2024 Annual Meeting, our shareholders overwhelmingly approved our executive compensation, with approximately 93% of the votes cast voting in favor of the “say-on-pay” proposal. The results of the say-on-pay vote indicate strong shareholder support of our compensation and pay decisions made in relation to our performance.

Our Board of Directors is asking shareholders to approve a non-binding advisory vote on the following resolution:

RESOLVED, that the compensation paid to the Company’s Named Executive Officers, as disclosed pursuant to the compensation disclosure rules of the SEC, including the Compensation Discussion and Analysis, the compensation tables, and any related material disclosed in this proxy statement, is hereby approved.

This vote on the compensation of our Named Executive Officers is advisory, and therefore not binding on the Company, the Compensation Committee, or our Board of Directors. Our Board of Directors and our Compensation Committee value the opinions of our shareholders and, to the extent there is any significant vote against the Named Executive Officers’ compensation as disclosed in this proxy statement, we will consider our shareholders’ concerns and the Compensation Committee will evaluate whether any actions are necessary to address those concerns.

THE BOARD OF DIRECTORS BELIEVES THAT THE PROPOSAL TO APPROVE, ON A NON-BINDING ADVISORY BASIS, THE EXECUTIVE COMPENSATION CONTAINED IN THIS PROXY STATEMENT IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” THIS PROPOSAL.

PROPOSAL 6 – RATIFICATION OF SELECTION OF INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM

Our Audit Committee has selected PricewaterhouseCoopers LLP, or PwC, as the Company’s independent registered public accounting firm for the fiscal year ending December 31, 2025. PwC was our independent registered public accounting firm for the fiscal year ended December 31, 2024.

Representatives of PwC have been invited to and are expected to attend the 2025 Annual Meeting. They will have the opportunity to make a statement if they so desire and will be available to respond to appropriate questions from shareholders. In the event that the ratification of the selection of PwC as our independent registered public accounting firm is not obtained at the 2025 Annual Meeting, the Board of Directors will reconsider its appointment.

THE BOARD OF DIRECTORS BELIEVES THAT THE PROPOSAL TO RATIFY THE SELECTION OF PWC AS OUR INDEPENDENT REGISTERED PUBLIC ACCOUNTING FIRM FOR THE FISCAL YEAR ENDING DECEMBER 31, 2025 IS IN THE BEST INTERESTS OF MKS AND OUR SHAREHOLDERS AND THEREFORE RECOMMENDS A VOTE “FOR” THIS PROPOSAL.

CORPORATE GOVERNANCE

Board Independence

The Board of Directors has determined that all of the members of the Board of Directors, other than Dr. Lee, are independent as defined under applicable Nasdaq rules. Dr. Lee is not independent as he currently serves as our President and Chief Executive Officer.

Board Leadership Structure

Since 2005, we have separated the roles of Chief Executive Officer and Chair of the Board of Directors in recognition of the differences between the two roles. The Chief Executive Officer is responsible for setting the strategic direction of the Company and the day-to-day leadership and performance of the Company, while the Chair of the Board of Directors provides guidance to the Chief Executive Officer, sets the agenda for Board meetings, and presides over meetings of the Board of Directors.

In addition, our Corporate Governance Guidelines provide that during any period in which the Chair of the Board of Directors is not an independent director, and in such other instances as the Board of Directors may determine from time to time, a Lead Director shall be elected by and from the independent directors. While our independent directors are not currently obligated under our Corporate Governance Guidelines to elect a Lead Director, as our Chair is independent, they have elected to continue to do so. Dr. Moloney has served as our Lead Director since 2020.

The primary role of the Lead Director is to serve as a liaison between the independent directors and the Chair of the Board of Directors and/or the Chief Executive Officer and to represent the independent directors, as appropriate. Pursuant to our Corporate Governance Guidelines, the Lead Director shall, among other matters:

Our Board of Directors believes that its leadership structure is appropriate at this time for our Company because it strikes an effective balance between management and independent leadership participation in the Board of Directors’ process.

Communications from Shareholders

The Board of Directors will give attention to written communications that are submitted by shareholders and will respond if appropriate. The Chair of the Nominating and Corporate Governance Committee, with the assistance of our General Counsel, is primarily responsible for monitoring communications from shareholders and for providing copies or summaries to the other directors as he or she considers appropriate. Communications are forwarded to all directors if they relate to important substantive matters and include suggestions or comments

that the Chair of the Nominating and Corporate Governance Committee considers to be important for the directors to know. In general, communications relating to corporate governance and long-term corporate strategy are more likely to be forwarded than communications relating to ordinary business affairs, personal grievances, and matters as to which we tend to receive repetitive or duplicative communications.

Shareholders who wish to send communications on any topic to the Board of Directors should address such communications to the Board of Directors in care of Kathleen F. Burke, Esq., Executive Vice President, General Counsel, and Secretary, MKS Instruments, Inc., 2 Tech Drive, Suite 201, Andover, MA 01810.

Code of Business Conduct and Ethics

We have adopted a Code of Business Conduct and Ethics that applies to all of our directors, officers, and employees (including the principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions), which is posted on our website at www.mks.com/corporate-governance under Corporate Governance Documents. We intend to disclose on our website any amendments to, or waivers for our executive officers or directors from, our Code of Business Conduct and Ethics.

Board’s Role in Risk Oversight

Management is responsible for the day-to-day management of risks the Company faces, while the Board of Directors, as a whole and through its committees, has the ultimate responsibility for the oversight of risk management. Senior management attends quarterly meetings of the Board of Directors, provides presentations on operations, including significant risks, and is available to address any questions or concerns raised by the Board of Directors. Additionally, our three standing Board committees assist the Board of Directors in fulfilling its oversight responsibilities in certain areas of risk. Pursuant to its charter, the Audit Committee coordinates the Board of Directors’ oversight of the Company’s internal controls over financial reporting, disclosure controls and procedures, and Code of Business Conduct and Ethics. The Audit Committee is also responsible for discussing the Company’s policies with respect to financial risk assessment and financial risk management and overseeing the steps management has taken with respect to data privacy and cybersecurity risk exposure. Management regularly reports to the Audit Committee on these areas. The Compensation Committee assists the Board of Directors in fulfilling its oversight responsibilities with respect to the management of risks arising from our compensation policies and programs as well as succession planning for our senior management. The Nominating and Corporate Governance Committee assists the Board of Directors in fulfilling its oversight responsibilities with respect to the management of risks associated with board organization, membership and structure, succession planning for our directors, corporate governance, and environmental, including climate-related, social, and governance risks. In addition, from time to time, the Board of Directors may constitute a special committee to focus on a particular matter or risk. When any of the committees receives a report related to material risk oversight, the chair of the relevant committee reports on the discussion to the full Board of Directors.

Transactions with Related Persons

Our Code of Business Conduct and Ethics sets forth the general principle that our directors, officers, and employees should refrain from engaging in any activity having a personal interest that presents a conflict of interest. Our Code of Business Conduct and Ethics prohibits directors, officers, and employees from engaging in any activity that may reasonably be expected to give rise to a conflict of interest or to adversely affect our interests. Our Code of Business Conduct and Ethics provides that all employees are responsible for disclosing to the Company any transaction or relationship that reasonably could be expected to give rise to a conflict of interest, and executive officers and directors must report such transactions to the Board of Directors, which shall be responsible for determining whether such transaction or relationship constitutes a conflict of interest.

In addition, our written Related Person Transaction Procedures set forth the procedures for reviewing transactions that could be deemed to be “related person transactions” (defined as transactions required to be disclosed pursuant to applicable SEC regulations). In accordance with these procedures, directors and executive officers are required to submit annual certifications regarding interests and affiliations held by them and certain of their family members. We then review our records to determine whether we have engaged in any transactions since the beginning of our prior fiscal year with such affiliated persons and entities or with any person or entity known by MKS to be the beneficial owner of more than 5% of our voting securities, and provide a summary to the Audit Committee of any such material transaction in which the related person has a direct or indirect interest. In

accordance with the procedures, the Audit Committee reviews any such transactions (including, but not limited to, transactions constituting related person transactions). In reviewing any such transaction, the Audit Committee considers, among other things, the related person’s interest in the transaction, the approximate dollar value of the transaction, whether the transaction was undertaken in the ordinary course of business, whether the terms of the transaction were at arm’s length, the purpose and potential benefits to the Company of the transaction, and whether the transaction is in the best interests of the Company. The Audit Committee may, in its sole discretion, impose such conditions as it deems appropriate in connection with any related person transaction. In accordance with the Audit Committee charter, the Audit Committee reviews the Related Person Transaction Procedures from time to time.

FMR LLC beneficially owned approximately 6% of the Company’s outstanding voting shares as of March 4, 2025, based on a filing it made with the SEC. Certain affiliates of FMR LLC provide the Company with recordkeeping and administrative services related to the Company’s stock plans, 401(k) plan, and health savings accounts for the Company’s employees. In 2024, the Company paid these affiliates of FMR LLC approximately $127,000 for these services. The service contracts for these services were negotiated at arm’s length. As part of our Related Person Transaction Procedures, our Audit Committee reviewed the foregoing relationship with FMR LLC.

Board of Director Meetings and Committees of the Board of Directors

The Board of Directors held six meetings in 2024. During 2024, each director attended all meetings of the Board of Directors and all meetings of all committees of the Board of Directors on which he or she served. Pursuant to our Corporate Governance Guidelines, directors are encouraged to attend our annual meeting of shareholders. All of the directors then serving on the Board of Directors attended the 2024 Annual Meeting.

The Board of Directors has established three standing committees — Audit, Compensation, and Nominating and Corporate Governance — each of which operates under a charter that has been approved by the Board of Directors. Each committee’s charter is posted on our website at www.mks.com/corporate-governance under Corporate Governance Documents.

Audit Committee

The Audit Committee consists of Ms. Mora (Chair), Mr. Cannone, Mr. Donahue, and Mr. Jabre. Mr. Jabre joined the Audit Committee in November 2024 upon his appointment to the Board of Directors. The Board of Directors has determined that each of Ms. Mora, Mr. Cannone, Mr. Donahue, and Mr. Jabre is an “audit committee financial expert” as defined in applicable SEC regulations. Each member of the Audit Committee also meets the requirements for independence under applicable Nasdaq and SEC rules. The Audit Committee’s responsibilities include:

The Audit Committee held seven meetings in 2024.

Compensation Committee

The Compensation Committee consists of Mr. Batra (Chair), Dr. Moloney, and Ms. Mora. Each member of the Compensation Committee meets the requirements for independence under applicable Nasdaq and SEC rules. The Compensation Committee’s responsibilities include:

The Compensation Committee held six meetings in 2024. See the section below entitled “Executive Compensation — Compensation Discussion and Analysis” for further information about the role of the Compensation Committee and the scope of its activities.

Compensation Risk Assessment

Our Compensation Committee engaged its independent compensation consultant, Pearl Meyer & Partners, LLC, or Pearl Meyer, to conduct a risk assessment of our compensation programs and practices to understand if any risks exist that are reasonably likely to have a material adverse effect on our Company, and the results were reviewed by our Compensation Committee. Based on this assessment, our Compensation Committee concluded that our compensation programs and practices, as a whole, are appropriately structured and do not pose a material risk to our Company. Our compensation programs are intended to reward our executive officers and other employees for strong performance over the long-term, with consideration to short-term actions and results that strengthen and grow our Company. We believe our compensation programs provide the appropriate balance between short-term and long-term incentives, focusing on sustainable and profitable growth for our Company.

Compensation Committee Interlocks and Insider Participation

In 2024, Mr. Batra, Dr. Moloney, and Ms. Mora served on the Compensation Committee. None of the members of the Compensation Committee during 2024 were, at any time, officers or employees of MKS or our subsidiaries, and none of them had any relationship with us requiring disclosure under applicable SEC rules and regulations. None of our executive officers serves, or has served, as a member of the Board of Directors or Compensation Committee (or other committee serving an equivalent function) of any other entity which has one or more executive officers serving as a member of our Board of Directors or Compensation Committee.

Nominating and Corporate Governance Committee

The Nominating and Corporate Governance Committee consists of Dr. Moloney (Chair), Mr. Batra, and Ms. Warner. Upon Ms. Warner’s departure from the Board of Directors on May 12, 2025, Mr. Donahue is expected to join the Nominating and Corporate Governance Committee. Each member of the Nominating and Corporate Governance Committee meets the requirements for independence under applicable Nasdaq and SEC rules. The Nominating and Corporate Governance Committee’s responsibilities include:

The Nominating and Corporate Governance Committee held four meetings in 2024.

For information relating to the nomination of directors, see “Director Candidates” below.

Director Candidates

The Nominating and Corporate Governance Committee recommended to the Board of Directors that the director nominees, Dr. Lee and Dr. Moloney, be nominated by the Board of Directors for election as Class II Directors at the 2025 Annual Meeting. The Nominating and Corporate Governance Committee utilizes a number of processes to identify and evaluate director candidates, including the engagement of a third-party search firm and other resources to identify potential director candidates, as needed. For example, Mr. Jabre, who became a director in November 2024, was identified as a director candidate by a third-party search firm. Activities relating to identifying and selecting nominees include Board assessments of each incumbent director nominee for the current year, requests to Board members and others for recommendations of potential candidates, meetings from time to time to evaluate biographical information and background material relating to potential candidates, and interviews of selected candidates by the members of the Nominating and Corporate Governance Committee and other members of the Board of Directors.

In considering whether to recommend any particular candidate for inclusion in the Board of Directors’ slate of recommended director nominees, the Nominating and Corporate Governance Committee applies the criteria attached to the Company’s Corporate Governance Guidelines. These criteria include the candidate’s integrity, business acumen, knowledge of our business and industries, effectiveness, experience, diligence, conflicts of interest, and the ability to act in the interests of all shareholders. The Nominating and Corporate Governance Committee does not assign specific weights to particular criteria and no particular criterion is a prerequisite for each prospective nominee. The Nominating and Corporate Governance Committee also assesses the candidate’s professional background and skills against those of the existing Board members to ensure a breadth and diversity of expertise that suits the Company’s current and future business risks, industries, and challenges. See “Directors — Board Skills Matrix.” Nominees shall not be discriminated against on the basis of race, religion, national origin, sex, sexual orientation, disability, or any other basis proscribed by law. While the Nominating and Corporate Governance Committee does not have a formal policy with respect to diversity, the Board of Directors and the Nominating and Corporate Governance Committee believe that it is essential that the members of the Board of Directors represent diverse viewpoints, and the Nominating and Corporate Governance Committee actively seeks to have a diverse pool of candidates from which our Board of Director nominees are chosen. In considering candidates for the Board of Directors, the Nominating and Corporate Governance Committee considers the entirety of each candidate’s credentials in the context of these standards. We believe that the backgrounds and qualifications of our directors, considered as a group, should provide a composite mix of experience, knowledge, and abilities that will allow the Board of Directors to fulfill its responsibilities.

Shareholders may recommend individuals to the Nominating and Corporate Governance Committee for consideration as potential director candidates by submitting their names, together with appropriate biographical information and background material and a statement as to whether the shareholder or group of shareholders making the recommendation has beneficially owned at least $2,000 in market value or 1% of our Common Stock, whichever is less, for at least a year as of the date such recommendation is made, to the Nominating and Corporate Governance Committee, in care of Kathleen F. Burke, Esq., Executive Vice President, General Counsel, and Secretary, MKS Instruments, Inc., 2 Tech Drive, Suite 201, Andover, MA 01810. Assuming that appropriate biographical and background material has been provided on a timely basis, the Nominating and Corporate Governance Committee will evaluate shareholder-recommended candidates by following substantially the same process, and applying the same criteria, as it does in considering other candidates.

Shareholders also have the right under our By-Laws to directly nominate director candidates, without any action or recommendation on the part of the Nominating and Corporate Governance Committee or the Board of Directors, by following the procedures set forth under the heading “Deadline for Submission of Shareholder Proposals for the 2026 Annual Meeting” below.

ENVIRONMENTAL, SOCIAL, AND GOVERNANCE

Governance

Our environmental, social, and governance program and related management system is overseen by the Chief Executive Officer, or the CEO, and the Nominating and Corporate Governance Committee.

This program is supported by a cross-functional steering committee, which meets throughout the year, sets program strategy, defines annual objectives, provides guidance on high-level tactics to achieve its stated objectives, communicates to internal and external stakeholders, and monitors industry trends. In accordance with its charter, the Nominating and Corporate Governance Committee also reviews and reports to the Board of Directors on the Company’s strategy, goals, and initiatives in this area, including climate-related risks and opportunities as well as the impact of related issues on the Company.

In addition, our leadership approach is based on our commitment to conduct business with the highest standards of integrity. Our Code of Business Conduct and Ethics and our Human Rights and Labor Standards Policy are designed to ensure that we deliver on this commitment every day.

Human Capital Management

In order to compete and succeed in highly competitive markets and industries that are subject to rapid technological change, we believe it is critical to attract, motivate, and retain a dedicated, talented, and innovative team of employees. As part of these efforts, we strive to foster an inclusive and welcoming community, invest in continuous learning and development, engage meaningfully with employees, offer a competitive compensation and benefits program, and provide a safe and healthy workplace. We are committed to cultivating an inclusive environment where every individual is valued, respected, and empowered to bring their authentic selves to their work. This commitment stems from our belief that diverse viewpoints not only spur innovation but also fuel exceptional performance and sustainable progress. By embracing our global workforce’s unique backgrounds and perspectives, we strengthen our collective ability to innovate, collaborate and drive sustainable growth.

To further foster inclusion and belonging at MKS, we operate several initiatives. We recently launched programs — including cultural awareness workshops, book-read discussion groups, bias awareness trainings, and inclusive leadership sessions — to strengthen empathy, foster deeper cross-functional collaboration, and cultivate a workplace culture where every voice is heard and valued. We also recently launched two Employee Resource Groups, or ERGS — Veterans@MKS and Women@MKS. While these ERGs focus on the unique experiences of these groups, they are open to all employees who want to connect, learn and contribute to a culture of belonging at MKS. Our recruitment and selection procedures are bolstered by our MKS Hiring Guide & Toolkit, which is designed to attract top talent while mitigating potential bias. Consistent with our Corporate Governance Guidelines, we actively seek diverse candidates for the pool from which our Board of Director nominees are chosen. We also routinely conduct comprehensive analyses of pay practices in our major regions of operations to identify and, if necessary, rectify any disparities promptly and effectively. Our most recent global compensation analysis has resulted in equitable pay for our workforce with minimal adjustments.

MKS remains steadfast in its dedication to fostering learning and professional growth. We offer our employees a comprehensive catalog of programs, courses, and resources aimed at building leadership capabilities and personal effectiveness. Our performance management framework is designed to provide ongoing, actionable feedback, and facilitate dynamic career development conversations throughout the year. In 2024, we launched a global mentorship program designed to connect our employees across all regions and functions and build mentor and mentee relationships that focus on continuous learning and development. This program reflects our commitment to investing in our people and promoting a culture of growth and development. We also extend financial assistance for higher education to eligible employees, including support for college and graduate studies. In addition, we ensure accessibility to online learning resources via LinkedIn Learning for all employees, cultivating professional development.

In 2024, we conducted our fourth annual global employee engagement survey, with a record 88% participation rate. The survey findings were analyzed and shared with our President and CEO, the executive leadership team, and our Board of Directors. Comprehensive communication of the results was extended to all employees and supplemented with executive videos and both in-person and virtual focus groups to pinpoint prevailing themes. Leveraging these themes and data points, tailored action items were created to encourage meaningful change, with corporate initiatives focusing on communication, innovation, and inclusion.

MKS is also committed to providing total compensation packages that attract, motivate, and retain our employees, as well as recognizing and rewarding our employees’ sustained performance and results. In addition, we are committed to ensuring that our total compensation packages are externally competitive and internally equitable, while supporting our business plans and strategies. As employee turnover is an indicator of employee

satisfaction, we monitor turnover globally. MKS has a very stable and committed workforce, as evidenced by low voluntary turnover. Our voluntary turnover for the year ended December 31, 2024 was below 7%. Our average employee tenure as of December 31, 2024 was more than 10 years.

Health & Safety

MKS is committed to providing a safe and healthy workplace for all employees. We accomplish this through compliance with applicable laws and regulations regarding workplace safety, including recognition and control of workplace hazards, tracking injury and illness rates, utilizing a global travel risk management program, and maintaining detailed emergency and business continuity plans. We also provide mandatory environmental, health, and safety training to ensure all employees are provided with the education to perform their jobs safely and to protect the environment. In addition, we offer employees and eligible family members a full range of health and wellness programs, as well as many clinical and administrative services.

We have instituted MEHS, a formal Global MKS Management System for Environmental, Health, and Safety, to protect our employees, other stakeholders, and the environment. We continue to implement this strong foundation across our organization in a stepwise process.

Environmental Management

We play an integral part in delivering enabling solutions in an increasingly connected world. This position provides us with an opportunity to make an impact in furthering not just our own sustainability goals but also those of our customers. We are committed to operating our business in an environmentally and socially responsible manner, in tandem with our employees, customers, suppliers, and communities.

Our products are used in a broad range of industries and applications. Our ability to innovate is critical to achieving and sustaining product differentiation as well as establishing and deepening customer relationships. These innovations have accelerated roadmaps for customers in our primary markets and contributed to driving positive environmental impact and progress, including with respect to clean energy, renewable energy, and other sustainable, ethical applications.

As reported in our 2024 Environmental, Social, Governance Report, we committed to reduce our combined Scope 1 and 2 emissions by 42% by 2030 from our 2022 baseline, in alignment with criteria established by the Science Based Targets initiative, or SBTi. Once we determine our Scope 3 emissions targets, we will submit all of these climate goals to SBTi to be validated against SBTi guidance. As a first step to setting SBTi-aligned Scope 3 emissions targets, we conducted a scope 3 screening analysis to determine Scope 3 categories relevant to our business and are working to develop our consolidated Scope 3 emissions inventory. Once we determine our Scope 3 emissions targets, we will submit these climate goals to SBTi to be validated against SBTi guidance.

Additional information regarding MKS’ activities related to its people and sustainability can be found in our 2024 Environmental, Social, Governance Report, which is accessible through our website at www.mks.com/environmental-social-governance. Our Environmental, Social, Governance Report is updated periodically.

DIRECTOR COMPENSATION

Cash Compensation

The following table summarizes the cash compensation payable by us to non-employee directors in 2024:

Retainers are pro-rated based on the time a director serves in the capacities listed. In addition, from time to time, the Board of Directors may form special committees related to specific matters and may elect to compensate directors for their service on such committees on a fee-per-meeting basis or with a retainer.

Equity Compensation

Non-employee directors are eligible for awards under our 2022 Stock Incentive Plan, which is administered by the Compensation Committee. In 2024, under our director compensation program, non-employee directors received automatic grants of restricted stock units, or RSUs, on the date of the 2024 Annual Meeting, with a grant date value of $200,000, which RSUs will vest in full on the day prior to the 2025 Annual Meeting. In November 2024, our Board of Directors, upon the recommendation of the Compensation Committee, increased the value of the annual RSU grant to $225,000 for each non-employee director, effective January 1, 2025. Our Compensation Committee recommended this increase after reviewing a competitive analysis of director compensation programs, which was prepared by the Compensation Committee’s independent compensation consultant, Pearl Meyer. The analysis found that the equity compensation and total compensation paid to non-employee members of our Board fell below the median of our peer group.

In addition, in 2024, under our director compensation program, if a new non-employee director joined our Board of Directors after our annual meeting of shareholders but before January 1st of the following year, he or she was entitled to an initial RSU grant with a value equal to the annual RSU grant. In the event a non-employee director joined our Board of Directors during the period from January 1st through the date of that year’s annual meeting of shareholders, he or she was not entitled to an initial RSU grant but was entitled to the annual RSU grant on the date of the annual meeting of shareholders. In November 2024, our Board of Directors, upon the recommendation of the Compensation Committee, amended our director compensation program, effective January 1, 2025, so that if a new non-employee director joins our Board of Directors other than in connection with an annual meeting of shareholders, he or she will be entitled to an initial RSU grant with a value equal to the annual RSU grant, pro-rated based on the effective date of his or her appointment.

Director Compensation Table for 2024

The following table summarizes compensation earned by or paid to non-employee directors in 2024. Dr. Lee is excluded from the table because he is an executive officer and his compensation is set forth in the Executive Compensation section below, under the heading “Executive Compensation Tables — Summary Compensation Table for 2024.”

AUDIT AND FINANCIAL ACCOUNTING OVERSIGHT

Audit Committee Report

The Audit Committee of our Board of Directors has reviewed our audited financial statements for the year ended December 31, 2024 and discussed them with our management.

The Audit Committee discussed with PricewaterhouseCoopers LLP, or PwC, our independent registered public accounting firm, the matters required to be discussed by the applicable requirements of the Public Company Accounting Oversight Board and the SEC.

The Audit Committee has received the written disclosures and the letter from our independent registered public accounting firm required by the applicable requirements of the Public Company Accounting Oversight Board regarding the independent accountant’s communications with the Audit Committee concerning independence, and has discussed with the independent accountant the independent accountant’s independence.

Based on the review and discussions referred to above, the Audit Committee recommended to our Board of Directors that the audited financial statements be included in our Annual Report on Form 10-K for the year ended December 31, 2024.

Respectfully submitted,

Elizabeth A. Mora, Chair

Peter J. Cannone III

Joseph B. Donahue

Wissam G. Jabre

Principal Accountant Fees and Services

For the years ended December 31, 2024 and 2023, aggregate fees for professional services rendered by our independent registered public accounting firm, PwC, in the following categories were as follows:

Audit Fees

Audit fees billed for both years consisted of fees for professional services rendered for: (i) the audit of our annual consolidated financial statements, (ii) statutory audits, (iii) the review of our consolidated financial statements included in our quarterly reports on Form 10-Q, (iv) audit services related to other reports filed with the SEC, and (v) the audit of our internal controls over financial reporting as required by the rules and regulations promulgated under Section 404 of the Sarbanes-Oxley Act of 2002.

Audit-Related Fees

There were no audit-related fees for the years ended December 31, 2024 and 2023.

Tax Fees

Tax fees for the years ended December 31, 2024 and 2023 were for services related to tax compliance, including the preparation of tax returns, and tax planning and tax advice, including assistance with foreign operations and foreign tax audits.

All Other Fees

All other fees for the years ended December 31, 2024 and 2023 were for accounting research software.

In 2024 and 2023, all fees for professional services rendered by our independent registered public accounting firm were pre-approved pursuant to the Audit Committee’s pre-approval requirements, described below.

Pre-Approval Policy and Procedures

The Audit Committee’s charter sets forth the Audit Committee’s obligations relating to the approval of all audit and non-audit services that are to be performed by our independent registered public accounting firm. The charter provides that we will not engage our independent registered public accounting firm to provide audit or non-audit services unless the service is pre-approved by the Audit Committee. In addition, we will not engage any

other accounting firm to provide audit services unless such services are pre-approved by the Audit Committee. It is the Audit Committee’s policy that with respect to services performed or to be performed by PwC in connection with each fiscal year of the Company, the annual fees for non-audit services in such year shall not exceed one half of the aggregate fees payable to PwC for such year, without the prior express approval of the Audit Committee.

In connection with the foregoing, the Audit Committee may approve specific services in advance. In addition, from time to time, the Audit Committee may pre-approve specified types of services that are expected to be provided to us by our independent registered public accounting firm during the next 12 months. Any such pre-approval of types of services is detailed as to the particular service or type of service to be provided and is also generally subject to a maximum dollar amount.

The Audit Committee has also delegated to the Chair of the Audit Committee the authority to approve any audit or non-audit services to be provided to us by our independent registered public accounting firm. Any approval of services by the Chair of the Audit Committee pursuant to this delegated authority is reported on at the next meeting of the Audit Committee.

The Audit Committee has considered and determined that the provision of the non-audit services noted in the foregoing table is compatible with maintaining PwC’s independence.

SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT

The following table sets forth certain information with respect to the beneficial ownership of our Common Stock by (i) each shareholder known to us to be the beneficial owner of more than 5% of the outstanding shares of our Common Stock; (ii) the Named Executive Officers named in the Summary Compensation Table below; (iii) each of our current directors; and (iv) all of our directors and executive officers as a group. Unless otherwise indicated in the footnotes to the table, all equity amounts set forth in the table are as of March 4, 2025. The address for each of our directors and executive officers is: c/o MKS Instruments, Inc., 2 Tech Drive, Suite 201, Andover, Massachusetts 01810.

To our knowledge, there are no voting trusts or similar arrangements among any of the foregoing persons or entities with respect to the voting of shares of Common Stock.

EXECUTIVE OFFICERS

The following is a brief summary of the background of each of our current executive officers, other than Dr. Lee, whose background is described under the heading “Directors” above.

Executive Officer				Background and Qualifications
		Ramakumar Mayampurath, 61   Executive Vice President, Chief Financial Officer, and Treasurer		Mr. Mayampurath has served as Executive Vice President, Chief Financial Officer and Treasurer since October 2024. Prior to joining MKS, he served as Senior Vice President and Chief Financial Officer of Rogers Corporation, a global leader in engineered materials, from May 2021 to August 2024. During his tenure as Senior Vice President and Chief Financial Officer of Rogers, Mr. Mayampurath also served as Treasurer from May 2021 to September 2021 and from June 2022 to August 2024. He previously served in various other senior roles at Rogers, including Vice President, Corporate Finance from December 2020 to April 2021, Vice President, Business Transformation from March 2020 to December 2020, Vice President, Global Financial Planning & Analysis from April 2016 to March 2020, and Vice President, Corporate, Financial Planning & Analysis and Treasurer from November 2014 to March 2016. Prior to joining Rogers, Mr. Mayampurath served in divisional financial leadership roles at Royal Philips Electronics from 2005 to 2014. He is a chartered accountant (inactive) and holds an M.B.A. from Southern Illinois University and a Master of Global Management from Thunderbird School of Global Management.
		Kathleen F. Burke, 60   Executive Vice President, General Counsel, and Secretary		Ms. Burke has served as Executive Vice President, General Counsel, and Secretary since February 2023. From May 2017 to February 2023, she served as Senior Vice President and General Counsel, becoming Secretary in May 2019. From April 2011 to May 2017, she served as Vice President and General Counsel, and from January 2005 to May 2019, she served as Assistant Secretary. From January 2005 to April 2011, Ms. Burke served as General Counsel, and from February 2004 to January 2005, she served as Corporate Counsel. Prior to joining MKS, Ms. Burke was a corporate attorney at Wilmer Cutler Pickering Hale and Dorr LLP (formerly Hale and Dorr LLP), a full-service international law firm, from 1994 to 2004. Ms. Burke served as a member of the Board of Directors of the Northeast Chapter of the Association of Corporate Counsel, a global legal association, from 2009 to 2020 and served as the Chapter’s President from 2011 to 2013, its Vice President from 2010 to 2011 and its Treasurer from 2009 to 2011. Ms. Burke holds a B.A. from Boston College and a J.D. from Boston College Law School.

Executive Officer				Background and Qualifications
		Eric R. Taranto, 57   Executive Vice President and General Manager, Vacuum Solutions Division		Mr. Taranto has served as an Executive Vice President since February 2023 and General Manager, Vacuum Solutions Division since November 2020. From November 2020 to February 2023, he served as a Senior Vice President. From September 2014 to November 2020, he served as Vice President and General Manager of Business Units in our Vacuum & Analysis Division (now known as our Vacuum Solutions Division). From July 2014 to December 2020, he was also a member of our Office of the Chief Technology Officer (OCTO), and he chaired the OCTO from January 2018 to December 2020. From September 2000 to September 2014, Mr. Taranto served in a range of managerial and senior engineering positions at MKS. From December 1997 to September 2000, he served as a senior engineer for D.I.P. Inc., a digital-control network supplier, until it was acquired by MKS in September 2000.
		John E. Williams, 56   Executive Vice President and General Manager, Photonics Solutions Division		Mr. Williams has served as Executive Vice President and General Manager, Photonics Solutions Division since May 2024. From April 2020 to May 2024, he served as Vice President and General Manager of the Equipment Solutions Division (which became part of the Photonics Solutions Division in 2022). He joined MKS in February 2019 with the acquisition of ESI, where he served as Vice President of Marketing. Prior to joining ESI, Mr. Williams was Vice President of Corporate & Strategic Marketing at FEI, which became part of Thermo Fisher Scientific in 2016. Earlier in his career, he held various marketing and product management positions at leading capital equipment companies, including Lam Research Corporation and Brooks Automation, Inc. Mr. Williams holds a B.S. in Mechanical Engineering from California Polytechnic State University – San Luis Obispo.

Our executive officers are appointed by the Board of Directors on an annual basis and serve until their successors are duly appointed and qualified. There are no family relationships among any of our executive officers or directors.

EXECUTIVE COMPENSATION

Compensation Discussion and Analysis

Introduction

The purpose of this section of our proxy statement is to provide an overview of our executive compensation program, our compensation philosophy and objectives, and the material decisions we made with respect to each element of our executive compensation program. Throughout this proxy statement, we refer to the “2024 Named Executive Officers” listed below.

Ramakumar Mayampurath was appointed Executive Vice President, Chief Financial Officer, and Treasurer, effective October 14, 2024. He succeeded Seth H. Bagshaw, who provided notice to us in December 2023 that he would retire as Executive Vice President, Chief Financial Officer, and Treasurer effective April 1, 2024, following 18 years of service with our Company. Following his retirement from this role, Mr. Bagshaw remained employed as a special advisor from April 1, 2024 until May 1, 2024. In light of his retirement, Mr. Bagshaw did not receive a salary increase, annual cash incentive compensation opportunity, or long-term equity incentive compensation for 2024. Mr. Bagshaw’s salary in effect as of the date of his notice of retirement was paid through May 1, 2024. See “Executive Compensation Tables — Summary Compensation Table.” As a result, no compensation discussions or decisions were made with respect to Mr. Bagshaw during 2024. Therefore, Mr. Bagshaw is not included in the discussion below. We refer to our 2024 Named Executive Officers who did serve through December 31, 2024 as the “Named Executive Officers” throughout this Compensation Discussion and Analysis.

Following this Compensation Discussion and Analysis, you will find a series of tables containing specific information about the compensation earned by or paid to our 2024 Named Executive Officers in 2024.

Executive Summary

Our Business

We enable technologies that transform our world. We deliver foundational technology solutions to leading edge semiconductor manufacturing, electronics and packaging, and specialty industrial applications. We apply our broad science and engineering capabilities to create instruments, subsystems, systems, process control solutions, and specialty chemicals technology that improve process performance, optimize productivity, and enable unique innovations for many of the world’s leading technology and industrial companies. Our solutions are critical to addressing the challenges of miniaturization and complexity in advanced device manufacturing by enabling increased power, speed, feature enhancement, and optimized connectivity. Our solutions are also critical to addressing ever-increasing performance requirements across a wide array of specialty industrial applications.

Company Performance in 2024

In 2024, we achieved improvements in gross margins, operating income, net income per share, and operating cash flow compared to 2023, despite a muted demand environment across our end markets. Our performance was enabled by our broad and deep technology portfolio, which allowed us to balance demand softness in certain markets with growth in others. We generated strong gross margins that demonstrate the value our customers place on our products and capabilities. We also carefully managed operating expenses to maintain overall profitability and solid cash generation.

In addition, we took several actions to proactively manage our leverage and significantly reduce our interest expense. In 2024, we (i) completed an upsized $1.4 billion convertible notes offering, substantially all of the proceeds of which were used to pay down $1.2 billion of our existing USD term loan B and purchase $167 million of capped calls, (ii) made voluntary prepayments of $426 million on our term loan facility, and (iii) executed a favorable refinancing and repricing of our term loans. We took these actions while maintaining investments in research and development and strategic initiatives, including upgrading and expanding our operations in Romania, breaking ground on our new super center factory in Penang, Malaysia, and purchasing a site for a chemistry factory and tech center in Thailand.

In our Semiconductor market, revenue modestly increased in 2024, constrained by continued softness in semiconductor capital equipment spending, including a pronounced downturn in NAND investment. Our teams remain closely engaged with equipment OEMs and leading semiconductor fabs in addressing a broad range of technology inflections, including in growing markets such as lithography, metrology, and inspection, where we are advancing our strategy to grow segment share. We achieved strategic design wins and secured new customer orders through our World Class Optics initiative, highlighting our increasingly differentiated technology.

Revenue in our Electronics & Packaging market slightly increased in 2024, driven by an increase in industry demand for printed circuit board, or PCB, via drilling systems. While overall demand remained muted, we saw encouraging order activity for our chemistry and equipment solutions for advanced multi-layer board, high-density interconnect, and package substrates related to artificial intelligence applications. We have demonstrated to a wide variety of customers how our combined laser and chemistry capabilities can drive new growth opportunities for their businesses. We achieved a number of design wins, including synergistic wins that have introduced chemistry customers to our laser products and laser customers to our chemistry products.

Sales from our Specialty Industrial market declined in 2024, due to lower solar, general industrial, and material processing sales. Our strategy in Specialty Industrial is to leverage our technology investments in our Semiconductor and Electronics & Packaging markets into niche applications that create market leadership opportunities and generate attractive incremental cash flows.

For a second straight year, our emphasis on corporate responsibility resulted in MKS being recognized as one of America’s Most Responsible Companies for 2025 presented by Newsweek and Statista and a 2025 Best Company to Work For by U.S. News & World Report. We also released our fourth annual Environmental, Social, and Governance Report and were recognized in Sustainalytics’ 2024 list of ESG Top-Rated Companies, demonstrating our continued focus on sustainability.

In 2024, key financial and operating achievements include:

2024 Compensation Outcomes

Our executive compensation program is designed to reward our Named Executive Officers for performance and to align their interests with those of our shareholders. As a result of our financial performance in 2024, our Named Executive Officers received 30% of their target variable cash compensation under our Management Incentive Plan, which was measured against two financial metrics – non-GAAP operating income and adjusted net debt – and 51% of the portion of their target performance-based equity compensation measured against Adjusted EBITDA, which vests in equal annual installments over three years beginning in February 2025 (each financial metric as further described under “Elements of Compensation” below). We believe these financial metrics are important to our shareholders because each of non-GAAP operating income and Adjusted EBITDA is an indicator of how well we manage the operations and profitability of our Company and adjusted net debt is an indicator of how well we manage our significant debt. The alignment of our financial performance goals with our incentive payout opportunities for 2024 is evidenced by the fact that our Management Incentive Plan and our performance-based equity awards subject to Adjusted EBITDA each paid out well below 100% achievement in a year where our Named Executive Officers needed to achieve “stretch” targets to earn their target performance-based compensation. Although we executed well amid a muted demand environment, we were unable to achieve our stretch targets.

Consideration of 2024 Advisory Vote on Executive Compensation

At our 2024 Annual Meeting, held on May 7, 2024, we submitted to our shareholders an advisory vote on executive compensation. Although annual advisory say-on-pay votes are non-binding, our Compensation Committee considers the outcome of this vote each year when making compensation decisions for our Named Executive Officers. At the 2024 Annual Meeting, our shareholders overwhelmingly approved our executive compensation, with approximately 93% of the votes cast voting in favor of the say-on-pay proposal. The results of the say-on-pay vote indicate strong shareholder support of our compensation and pay decisions made in relation to our performance.

In addition to the results of the say-on-pay vote, the Compensation Committee considers evolving best practices, market compensation information, changing regulatory requirements, and the overall business environment when reviewing our executive compensation program. Based on this review, the Compensation Committee made material changes to our executive compensation program in 2024 by introducing a new metric under our Management Incentive Plan, adjusted net debt, in recognition of our current business strategy of paying down the debt we incurred in connection with our acquisition of Atotech, or the Atotech Acquisition, and introducing a new metric under our long-term equity incentive compensation program, relative total shareholder return, or rTSR, with a three-year measurement period to foster further alignment of executive and shareholder interests. See “Elements of Compensation — Annual Cash Incentive Compensation” and “Elements of Compensation — Long-Term Equity Incentive Compensation” below for more information about these changes.

Compensation Philosophy and Objectives

The primary objectives of our executive compensation program are to:

We target each of our Named Executed Officers’ various compensation elements, including base salary, annual cash incentive compensation, and long-term equity incentive compensation, to be within a competitive range around median levels (plus or minus 15% of median) for each such respective position in the market. The

competitive range is considered alongside other key factors when setting compensation levels, and final values for each of our Named Executive Officers may range from approximately the 25^th percentile to approximately the 75^th percentile. In considering the compensation of our Named Executive Officers relative to the market, we also qualitatively assess each Named Executive Officer’s overall performance, tenure, and potential contributions to MKS’ ongoing growth. For 2024, the total target compensation for each of Dr. Lee, Ms. Burke, Mr. Henry, and Mr. Schreiner fell between the 30^th and 55^th percentile of our peer group.

As discussed above, Mr. Mayampurath joined the Company in October 2024, and we entered into an employment agreement with him that set forth his compensation for 2024. This compensation was determined through negotiations and aligned with market standards necessary to secure his employment. Mr. Mayampurath’s base salary for 2024 fell within the competitive range of the median of our peer group. Mr. Mayampurath did not receive an annual cash incentive compensation opportunity or performance-based long-term equity incentive compensation for 2024. However, Mr. Mayampurath received (i) a one-time sign-on cash bonus of $1,000,000, subject to repayment if Mr. Mayampurath voluntarily resigns or his employment is terminated for cause, each prior to the second anniversary of his start date, and (ii) a one-time sign-on equity award with a grant date value of $1,750,000 in the form of time-based RSUs, which were granted on November 15, 2024 and vest in two equal annual installments. For additional information regarding Mr. Mayampurath’s compensation and the terms of his employment agreement, see “Executive Compensation Tables — Potential Payments Upon Termination or Change-in-Control — Other Named Executive Officers” below.

Base salaries are designed to provide executives with a level of predictability and stability with respect to a portion of their total compensation package. Base salaries are a relatively small component of the overall pay packages of our Named Executive Officers because we believe a significant majority of executive compensation should be variable and based on performance.

Our annual cash incentive compensation program is designed to reward the attainment of short-term earnings goals that drive the long-term growth of MKS. We believe that these goals are aligned with significant value creation, and that our plan creates a strong link between pay and performance while providing a meaningful incentive for our Named Executive Officers to deliver financial results that exceed our goals.

We provide our Named Executive Officers with long-term equity incentive compensation in the form of RSUs, at least half of which are performance-based, in order to:

In order to further underscore our compensation values and enhance the efficacy of our pay programs, we also adhere to the following practices:

What We Do

What We Do Not Do

The following charts show the components of total target compensation on a percentage basis for our Chief Executive Officer and our other Named Executive Officers (excluding Mr. Mayampurath) as a group for 2024.

In May 2023, the Compensation Committee reviewed the peer companies to be used to determine 2024 executive compensation, which at that time consisted of 18 U.S. publicly traded companies that had been primarily selected based on similar industry and size. In determining whether these peer companies should continue to be included in the peer group, the Compensation Committee considered whether these peer companies had (i) a revenue range relative to our projected 2023 revenue between approximately 0.5 to 2.0 times, (ii) a market capitalization range relative to our average market capitalization for the twelve months ended December 31, 2022 between approximately 0.3 and 3.0 times, and (iii) an employee headcount relative to our employee headcount as of December 31, 2022 between approximately 0.5 to 2.0 times. The Compensation Committee also considered secondary factors, including other relevant peer groups, other performance considerations, and whether a company is a competitor for talent. The only change the Compensation Committee elected to make was to remove Revvity, Inc. (formerly PerkinElmer, Inc.) from the existing peer group because of a recent divestiture it made that resulted in no industry overlap with MKS. As a result, publicly available compensation data from the following 17 peer companies was used in determining executive compensation for 2024:

In certain instances where robust peer group benchmark data was not available, our Compensation Committee utilized size and industry-appropriate broad survey data from the Radford Global Compensation Database.

Elements of Compensation

The following summarizes the compensation elements for our Named Executive Officers:

Base Salary

When our Compensation Committee set 2024 annual executive compensation in February 2024, the Compensation Committee approved salary increases of 5.3% for Dr. Lee and approximately 3% for each of Ms. Burke, Mr. Henry, and Mr. Schreiner. The effective date of these increases was delayed from April 2024 until August 2024, consistent with a Company-wide initiative to control costs.

Listed below is the base salary our Compensation Committee approved for Dr. Lee, our President and Chief Executive Officer, in 2023 and 2024.

Listed below are the base salaries our Compensation Committee approved for our other Named Executive Officers in 2023 and 2024.

Annual Cash Incentive Compensation

For 2024, our Compensation Committee modified our annual cash incentive program to better align with our current business strategy of paying down the debt we incurred in connection with the Atotech Acquisition. In 2023, cash bonus payouts under the Management Incentive Plan were based on one performance metric, non-GAAP operating income. Although the Compensation Committee continues to believe non-GAAP operating income serves as a barometer of our success, non-GAAP operating income, defined as our GAAP operating income excluding any charges or income not related to our operating performance, does not directly account for our debt levels, which increased substantially as a result of the Atotech Acquisition and may adversely affect us by increasing our interest expense and decreasing our business flexibility, among other things. Following discussions with management about the importance of generating strong cash flow to reduce our debt, in February 2024, our Compensation Committee determined that a portion of future cash bonus payouts to our Named Executive Officers should be based on a second performance metric, adjusted net debt, defined as our gross debt, less cash and short-term investments, adjusted for the impact of foreign currency changes and certain items that our Compensation Committee considers to be outside the ordinary course of operations. For 2024, cash bonus payouts were based on two performance metrics, (i) non-GAAP operating income, weighted at 70% of each Named Executive Officer’s Target Bonus Amount (as defined below), and (ii) adjusted net debt, weighted at 30% of each Named Executive Officer’s Target Bonus Amount.

Historically, achievement of our plan of record for a performance metric would result in a cash payout equal to 100% of a Named Executive Officer’s Target Bonus Amount for that performance metric. However, in order to address the expected continued softened business environment for 2024, drive increased profits, and reduce costs, our Compensation Committee determined that for 2024, achievement of our plan of record for a performance metric would result in a cash payout equal to 25% of a Named Executive Officer’s Target Bonus Amount for that performance metric. For a Named Executive Officer to receive a cash payout equal to 100% of his or her Target

Bonus Amount for a performance metric in 2024, the Company would need to achieve a “Stretch Target” beyond our plan of record for that performance metric.

Under the Management Incentive Plan, each Named Executive Officer (except Mr. Mayampurath) was eligible to receive a performance bonus based on a specified percentage of base salary earned during the 2024 calendar year. Any performance bonus under the Management Incentive Plan would be capped such that payout would not exceed an amount equal to 200% of the Named Executive Officer’s Target Bonus Amount.

In 2024, payouts under the Management Incentive Plan were determined by multiplying each Named Executive Officer’s “Target Bonus Amount” by the Company’s percentage achievement of non-GAAP operating income and adjusted net debt, as described below. Target Bonus Amount consists of each Named Executive Officer’s base salary earned in 2024, multiplied by his or her “Target Bonus Percentage,” as determined by our Compensation Committee. If a Named Executive Officer’s base salary and/or Target Bonus Percentage changed during 2024, the Named Executive Officer’s Target Bonus Amount was pro-rated based on the number of days in 2024 that the Named Executive Officer received such base salary and/or Target Bonus Percentage. When our Compensation Committee met in February 2024, it did not approve any changes to the Target Bonus Percentages for Dr. Lee, Ms. Burke, Mr. Henry, or Mr. Schreiner.

Listed below is the Target Bonus Percentage for each Named Executive Officer in 2023 and 2024.

For 2024, our Compensation Committee set (i) plan of record achievement for non-GAAP operating income at an amount that was greater than actual achievement in 2023 but less than target achievement in 2023 and (ii) Stretch Target achievement for non-GAAP operating income at an amount that was greater than both actual achievement and target achievement in 2023. Our Compensation Committee set plan of record achievement and Stretch Target achievement for adjusted net debt at an amount that was greater than actual achievement in 2023. The successful alignment of our financial performance goals with our incentive payout opportunities for 2024 is evidenced by the fact that our Management Incentive Plan paid out at 30% achievement in a year where our Named Executive Officers needed to achieve Stretch Targets to earn their Target Bonus Amount. Although we executed well amid a muted demand environment, we were unable to achieve our Stretch Targets.

Non-GAAP Operating Income Metric (70% Weighting): In 2024, Named Executive Officers (excluding Mr. Mayampurath) would receive the following percentage of their Target Bonus Amount tied to non-GAAP operating income under the Management Incentive Plan, with proportional payments for achievement in between the Threshold Bonus Amount and the Maximum Bonus Amount.

For purposes of the Management Incentive Plan, non-GAAP operating income was $776 million for 2024. As a result, Named Executive Officers (excluding Mr. Mayampurath) were eligible to receive 26% of their Target Bonus Amounts under this formula, or 18% when weighted at 70% of their overall cash bonus. In addition to excluding charges or income not related to our operating performance, the calculation of non-GAAP operating income for purposes of determining cash bonuses for 2024 excluded approximately $13 million associated with our Compensation Committee’s decision to adjust the payout of non-executive cash bonuses to 50% of target. We refer to this amount as the Non-Executive Bonus Adjustment. Our Compensation Committee excluded the Non-Executive Bonus Adjustment to neutralize the negative impact of this adjustment on the Named Executive

Officers’ cash bonuses, in order to foster non-executive employee retention and engagement without penalizing the Named Executive Officers. For a full reconciliation of 2024 operating income to 2024 non-GAAP operating income for purposes of the Management Incentive Plan, see Appendix C to this proxy statement.

Adjusted Net Debt Metric (30% Weighting): In 2024, Named Executive Officers (excluding Mr. Mayampurath) would receive the following percentage of their Target Bonus Amount tied to adjusted net debt under the Management Incentive Plan, with proportional payments for achievement in between the Threshold Bonus Amount and the Maximum Bonus Amount.

For purposes of the Management Incentive Plan, adjusted net debt was $3.76 billion as of December 31, 2024. As a result, Named Executive Officers (excluding Mr. Mayampurath) were eligible to receive 40% of their Target Bonus Amounts under this formula, or 12% when weighted at 30% of their overall cash bonus. For a full reconciliation of 2024 gross debt to 2024 adjusted net debt, see Appendix C to this proxy statement.

Listed below is the calculation of the combined payout under both metrics.

Listed below are our Named Executive Officers’ earned cash bonus payouts for 2024.

Long-Term Equity Incentive Compensation

When our Compensation Committee set 2024 annual executive compensation in February 2024, it awarded the following time-based and performance-based RSUs to our Named Executive Officers. The performance-based RSUs subject to Adjusted EBITDA, which account for 70% of our Named Executive Officers’ target performance-based RSUs, are subject to a one-year performance metric, and the performance-based RSUs subject to rTSR, which account for 30% of our Named Executive Officers’ target performance-based RSUs, are subject to a three-year performance metric, each as described below. The time-based RSUs vest in three equal annual installments from the original date of grant. The performance-based RSUs subject to Adjusted EBITDA vest in three equal annual installments from the original date of grant and the performance-based RSUs subject to rTSR vest in full on

or about the third anniversary of the original date of grant, in each case subject to achievement of the respective performance metric.

Listed below is the grant date value of the RSUs for each Named Executive Officer in 2023 and 2024.

With respect to performance-based RSUs, our goal is to select Company financial metrics that best align with our Company objectives. From 2020 to 2023, we used one performance metric, Adjusted EBITDA, defined as the Company’s GAAP operating income excluding any charges or income not related to the operating performance of the Company plus depreciation and stock compensation expense. We believe Adjusted EBITDA provides a clear indication of how effectively we manage the operations of our Company, while continuing to recognize the cyclical nature and volatility of the markets we serve, as well as to drive continued improvement in our Company’s operating model independent of revenue levels. Following a review of market practice, our Compensation Committee determined that a portion of performance-based RSUs awarded to our Named Executive Officers should be based on a second performance metric, rTSR, which is defined as the annualized rate of return of our stock (including appreciation in stock price and reinvestment of dividends) compared to the S&P 1500 Composite Electronic Equipment, Instruments & Components Index. Our Compensation Committee believes measuring a portion of performance-based RSU achievement using rTSR strengthens long-term alignment between executive and shareholder interests and elevates the performance orientation of our executive compensation program. For 2024, Dr. Lee, Ms. Burke, Mr. Henry, and Mr. Schreiner received two performance-based awards, one of which was subject to Adjusted EBITDA and accounted for 70% of his or her target performance-based RSUs and the other of which was subject to rTSR and accounted for 30% of his or her target performance-based RSUs.

Consistent with the modification to our Management Incentive Plan, our Compensation Committee also modified our long-term equity incentive compensation program. Historically, achievement of our plan of record for Adjusted EBITDA would result in 100% achievement of a Named Executive Officer’s performance-based RSUs. However, in order to address the expected continued softened business environment for 2024, drive increase profits, and reduce costs, our Compensation Committee determined that achievement of our plan of record for

Adjusted EBITDA would result in 25% achievement of a Named Executive Officer’s performance-based RSUs subject to Adjusted EBITDA for 2024. For a Named Executive Officer to receive 100% achievement of his or her performance-based RSUs subject to Adjusted EBITDA in 2024, the Company would need to achieve a “Stretch Target” beyond our plan of record for Adjusted EBITDA.

We choose to measure Adjusted EBITDA over a one-year performance period because of the cyclical nature and volatility of our markets, making it challenging to set multi-year performance targets, as evidenced by continued cyclical challenges in our end markets. To ensure our executive officers are focused on our Company’s long-term performance, the performance-based RSUs subject to Adjusted EBITDA vest in equal annual installments over three years from the original date of grant, subject to achievement of the performance metric. In addition, we choose to measure rTSR over a three-year performance period to further ensure executives are aligned with long-term shareholder interests.

We use RSUs as our form of equity incentive compensation because we believe RSUs help to ensure that our executive officers’ interests are aligned with our shareholders’ interests in both a rising and a declining stock market. We believe RSUs are preferable to stock options, which have a relatively high accounting cost as compared to their potential value to the executive officer, and restricted stock, which gives the executive officer voting and dividend rights prior to full vesting. Also, because RSUs are worth more than stock options on the date of grant, we are able to grant fewer RSUs as compared to stock options, resulting in less potential dilution to shareholders’ holdings.

In 2024, our Named Executive Officers would have forfeited all of their performance-based RSUs subject to Adjusted EBITDA if our Adjusted EBITDA was less than or equal to $553.2 million at an adjusted revenue level of $3.34 billion or if our Adjusted EBITDA was less than or equal to $831.7 million at an adjusted revenue level of $4.09 billion (with intermediate Adjusted EBITDA minimum thresholds at different adjusted revenue levels in between). If we achieved the plan of record for Adjusted EBITDA of $737.6 million at an adjusted revenue level of $3.34 billion or $1.11 billion at an adjusted revenue level of $4.09 billion (with proportional thresholds in between), then our Named Executive Officers would have received 25% of their target performance-based RSUs subject to Adjusted EBITDA. If we achieved the Stretch Target for Adjusted EBITDA of $848.2 million at an adjusted revenue level of $3.34 billion or $1.28 billion at an adjusted revenue level of $4.09 billion (with proportional thresholds in between), then our Named Executive Officers would receive 100% of their target performance-based RSUs subject to Adjusted EBITDA. If our Adjusted EBITDA was at or above $922.0 million at an adjusted revenue level of $3.34 billion or was at or above $1.39 billion at an adjusted revenue level of $4.09 billion (with proportional thresholds in between), then our Named Executive Officers would receive the maximum of 200% of their target performance-based RSUs subject to Adjusted EBITDA. If adjusted revenue was outside the range of $3.34 billion and $4.09 billion, then the performance target and payout would be calculated using the same payout formula. Proportional achievement levels would be made for Adjusted EBITDA between the minimum and maximum levels. If the percentage achievement for performance-based RSUs subject to Adjusted EBITDA was greater than 25% of the percentage achievement for the non-GAAP operating income metric of our annual cash incentive program, then our Compensation Committee could apply negative discretion with respect to the performance-based RSUs subject to Adjusted EBITDA up to an amount equal to the percentage achievement for the non-GAAP operating income metric. Our Compensation Committee believes the application of negative discretion under these circumstances helps foster appropriate alignment between pay and performance.

In 2024, because our adjusted revenue was $3.62 billion and our Adjusted EBITDA for purposes of determining performance-based RSU achievement was $927 million, our Named Executive Officers received 51% of their target performance-based RSUs subject to Adjusted EBITDA. In addition to excluding charges or income not related to our operating performance, the calculation of Adjusted EBITDA for purposes of determining performance-based RSU achievement for 2024 excluded the Non-Executive Bonus Adjustment, consistent with the adjustment made to the calculation of non-GAAP operating income for purposes of the Management Incentive Plan. For full reconciliations of 2024 revenue to 2024 adjusted revenue and 2024 net income to 2024 Adjusted EBITDA for purposes of determining performance-based RSU achievement, see Appendix C to this proxy statement.

The performance-based RSUs subject to rTSR that were granted to our Named Executive Officers in February 2024 will be measured over a three-year performance period from January 1, 2024 to December 31, 2026. rTSR for this performance period will be measured by comparing the 20-day trading day average of each of MKS and the S&P 1500 Composite Electronic Equipment, Instruments & Components Index at the beginning of the performance period against the respective 20-day trading day average at the end of the performance period.

Our Named Executive Officers will receive the following percentage achievement of their performance-based RSUs subject to rTSR (subject to certain caps discussed below), with proportional payments for achievement in between the Threshold Amount and the Maximum Amount.

Percentage achievement of the performance-based RSUs subject to rTSR is subject to two caps. First, if the Company has a negative absolute rTSR at the end of the performance period but is above the 50th percentile, eligible Named Executive Officers will receive no more than 50% of their target performance-based RSUs subject to rTSR. Second, the total value of the award at vest shall not exceed 8x the value of the award on the grant date.

Additional Information Regarding Equity Awards

It is our practice to make an initial equity-based grant to all of our Named Executive Officers at the time they commence employment in an amount that is consistent with amounts granted to other executive officers in the industry at similar levels of seniority. As discussed under “Compensation Philosophy and Objectives” above, Mr. Mayampurath received a one-time sign-on equity award with a grant date value of $1,750,000 in connection with his appointment as Executive Vice President, Chief Financial Officer, and Treasurer. We may also make equity-based grants to a Named Executed Officer in connection with a promotion or other change in position. In addition, we typically make an annual grant of equity-based compensation to our Named Executive Officers during the first fiscal quarter of each year. Discretionary equity-based awards may also be made during the year to provide an incentive to achieve a specific goal or to reward a significant achievement or for other reasons that the Compensation Committee determines.

As discussed under “Executive Compensation Tables — Potential Payments Upon Termination or Change-in-Control – Other Named Executive Officers” below, in May 2024, Mr. Schreiner and the Company entered into an amendment to Mr. Schreiner’s employment agreement with the Company to extend his expatriate service in Berlin, Germany for a third year and, in connection therewith, replace an expatriate service cash bonus in the amount of $500,000 that was due to be paid to him on or shortly after August 17, 2024 with an expatriate service equity award with a grant date value of $850,000 in the form of time-based RSUs, or the Expatriate RSUs. The Expatriate RSUs were granted on May 15, 2024, 60% of which vested on August 17, 2024 and 40% of which are scheduled to vest on August 18, 2025, subject to Mr. Schreiner’s continued expatriate service.

Perquisites

We do not offer perquisites. Our Compensation Committee believes this practice simplifies and more consistently aligns our compensation and benefits offerings for Named Executive Officers with other employees, while placing greater focus on performance-based compensation.

Severance and Change-in-Control Provisions

Each of our Named Executive Officers is entitled to certain payments and benefits in the event his or her employment terminates under specified circumstances as described in the applicable agreement and subject to his or her entry into a release of claims. In exchange for these payments and benefits, each of these officers has agreed to be restricted from competing with the Company during and following his or her termination of employment for a twelve-month period. In addition, RSU agreements with our Named Executive Officers with time-based vesting generally provide for acceleration of vesting in the event the executive’s employment is terminated without cause or the executive resigns for good reason within 24 months after a change-in-control event. RSU agreements with our Named Executive Officers with performance-based vesting based on Adjusted EBITDA provide for acceleration of vesting at target-level achievement in the event the executive’s employment is terminated without cause or the executive resigns for good reason within 24 months after a change-in-control event. RSU agreements with our Named Executive Officers with performance-based vesting based on rTSR provide

that the performance period for such shares shall end on the day prior to the closing date of a change in control, with the number of shares, if any, that would have vested on such date, as determined in accordance with the terms of such agreements, converting into time-based vesting RSUs subject to acceleration of vesting in the event the executive’s employment is terminated without cause or the executive resigns for good reason within 24 months after a change-in-control event. The severance and change-in-control provisions are designed to be competitive in the marketplace, to provide security for each of our Named Executive Officers in the event that we are acquired and his or her respective position is impacted, and to provide an incentive for our Named Executive Officers to stay with us through such a change-in-control event. These provisions are also intended to protect us from competitive harm by compensating our Named Executive Officers for agreeing to substantial non-compete provisions after employment termination. See “Executive Compensation Tables — Potential Payments Upon Termination or Change-in-Control” for more information about these agreements.

Compensation of our Chief Executive Officer

We entered into an employment agreement with Dr. Lee in November 2019 in connection with his promotion to Chief Executive Officer, effective as of January 1, 2020. The terms of Dr. Lee’s employment agreement reflected his role as the leader of our Company and the experience he brought to the position. For a detailed discussion of the material compensation terms of Dr. Lee’s employment agreement, including all amendments to this employment agreement, see “Executive Compensation Tables — Potential Payments Upon Termination or Change-in-Control.”

Compensation of our Other Named Executive Officers

We have entered into employment agreements with each of our other Named Executive Officers. For a detailed discussion of the material compensation terms of these executive employment agreements, including all amendments to these employment agreements, see “Executive Compensation Tables — Potential Payments Upon Termination or Change-in-Control.”

Compensation Consultant

We engage a compensation consultant to serve as an independent advisor to the Compensation Committee regarding compensation for our directors and our executive officers. The Compensation Committee utilizes the compensation consultant in the following ways:

Since May 2019, the Compensation Committee has engaged Pearl Meyer as its compensation consultant. The Compensation Committee has determined that the engagement of Pearl Meyer as a compensation consultant does not raise any conflicts of interest with MKS.