<SEC-DOCUMENT>0001127602-18-006783.txt : 20180216
<SEC-HEADER>0001127602-18-006783.hdr.sgml : 20180216
<ACCEPTANCE-DATETIME>20180216180529
ACCESSION NUMBER:		0001127602-18-006783
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20180215
FILED AS OF DATE:		20180216
DATE AS OF CHANGE:		20180216

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Werth Dennis L
		CENTRAL INDEX KEY:			0001550572

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23621
		FILM NUMBER:		18622471

	MAIL ADDRESS:	
		STREET 1:		1791 DEERE AVENUE
		CITY:			IRVINE
		STATE:			CA
		ZIP:			92606

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MKS INSTRUMENTS INC
		CENTRAL INDEX KEY:			0001049502
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		IRS NUMBER:				042277512
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		2 TECH DRIVE
		STREET 2:		SUITE 201
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		978-645-5500

	MAIL ADDRESS:	
		STREET 1:		2 TECH DRIVE
		STREET 2:		SUITE 201
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
</SEC-HEADER>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Unit</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F1"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2018-02-15</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1098</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F9"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F9"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>1098</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>16817.275</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Each restricted stock unit represents the contingent right to receive one share of common stock of MKS Instruments, Inc.</footnote>
        <footnote id="F2">This transaction was effected pursuant to a Rule 10b5-1 trading plan previously adopted by the reporting person.</footnote>
        <footnote id="F3">These RSUs are subject to the achievement of performance criteria determined in the first year of grant and thereafter vest in three equal annual installments beginning on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F4">These RSUs vest in three equal annual installments commencing on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F5">These RSUs are subject to the achievement of performance criteria determined in the first year of grant and thereafter vest in three equal annual installments beginning on February 15, 2018, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F6">These RSUs vest in three equal annual installments commencing on February 15, 2018, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F7">These RSUs are subject to the achievement of performance criteria determined in the first year of grant and thereafter vest in three equal annual installments beginning on February 15, 2017, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F8">These RSUs vest in three equal annual installments commencing on February 15, 2017, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
        <footnote id="F9">These RSUs vest in three annual installments as follows: 20% of the RSUs vests on February 15, 2017, 30% of the RSUs vests on February 15, 2018 and the remaining 50% of the RSUs vests on February 15, 2019, provided that if, in any vesting year, February 15th is not a business day, such vesting shall occur on the next business day.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ M. Kathryn Rickards, attorney-in-fact</signatureName>
        <signatureDate>2018-02-16</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
