<?xml version="1.0"?><ownershipDocument><schemaVersion>X0201</schemaVersion>    <documentType>4</documentType><periodOfReport>2003-08-22</periodOfReport><notSubjectToSection16>0</notSubjectToSection16><issuer><issuerCik>0000021535</issuerCik><issuerName>COHU INC</issuerName>        <issuerTradingSymbol>COHU</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001222023</rptOwnerCik><rptOwnerName>ALLEN JOHN H</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>12367 CROSTHWAITE CIRCLE</rptOwnerStreet1><rptOwnerStreet2></rptOwnerStreet2><rptOwnerCity>POWAY</rptOwnerCity><rptOwnerState>CA</rptOwnerState><rptOwnerZipCode>92064</rptOwnerZipCode><rptOwnerStateDescription></rptOwnerStateDescription></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>1</isOfficer><isTenPercentOwner>0</isTenPercentOwner><isOther>0</isOther><officerTitle>VP Finance &amp; CFO</officerTitle></reportingOwnerRelationship></reportingOwner><nonDerivativeTable><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-08-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>20000</value></transactionShares><transactionPricePerShare><value>12.07</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>38528</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeTransaction><nonDerivativeTransaction><securityTitle><value>Common Stock</value></securityTitle><transactionDate><value>2003-08-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>S</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>20000</value></transactionShares><transactionPricePerShare><value>21.68</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><postTransactionAmounts><sharesOwnedFollowingTransaction><value>18528</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></nonDerivativeTransaction></nonDerivativeTable><derivativeTable><derivativeTransaction><securityTitle><value>Employee Stock Option (Right to buy)</value></securityTitle><conversionOrExercisePrice><value>12.07</value></conversionOrExercisePrice><transactionDate><value>2003-08-22</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>M</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionTimeliness><value></value></transactionTimeliness><transactionAmounts><transactionShares><value>20000</value></transactionShares><transactionPricePerShare><value>12.07</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>D</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2000-03-10</value><footnoteId id="F1" /></exerciseDate><expirationDate><value>2009-03-10</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>20000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>30000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">The option vests in four equal annual installments beginning March 10, 2000</footnote></footnotes><remarks></remarks><ownerSignature><signatureName>/s/ John H. Allen</signatureName><signatureDate>2003-08-22</signatureDate></ownerSignature></ownershipDocument>

