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In the above formulae, L$_{1 }$ to L$_{4}$ , which are the same or different, each represents a hydrogen atom, a straight-chain, branched or cyclic alkyl group or an aralkyl group, and Z represents a straight-chain, branched or cyclic alkyl group or an aralkyl group. 

W has the same meaning as Z, and Zand Li, or Wand L$_{4}$, may be combined each other to form 5- or 6-membered ring, provided that the groups represented by Z and W are not the same. 

Examples of an alkyl group represented by each of L$_{1 }$ to L$_{4}$ , Z and W in the foregoing formulae include straight› chain, branched or cyclic alkyl groups containing 1 to 20 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, at-butyl group, a pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, an octyl group and a dodecyl group. These groups each may have a substituent. 

Suitable examples of a substituent the alkyl group repre- sented by L$_{1 }$ to L$_{4}$ , Zand W each may have include an alkyl group, an alkoxy group, a hydroxyl group, a halogen atom, a nitro group, an acyl group, an acyloxy group, an acylamino group, a sulfonylamino group, an alkylthio group, an arylthio group, an aralkylthio group, a thiophenecarbony- loxy group, a thophenemethyl carbonyloxy group, and het› ero ring residues, such as a pyrrolidone residue. And it is preferable that the number of carbon atoms contained in those substituents each is 12 or below. 

Examples of an alkyl group having a substituent include a cyclohexylethyl group, an alkylcarbonyloxymethyl group, an alkylcarbonyloxyethyl group, an arylcarbonyloxyethyl group, an aralkylcarbonyloxyethyl group, an alkyloxym› ethyl group, an aryloxymethyl group, an aralkyloxymethyl group, an alkyloxyethyl group, an aryloxyethyl group, an aralkyloxyethyl group, an alkylthiomethyl group, an arylthi› omethyl group, an aralkylthiomethyl group, an alkylthioet› hyl group, an arylthioethyl group and an aralkylthioethyl group. 

The alkyl moieties in the groups recited above have no particular restriction, but may be any of straight-chain, cyclic and branched ones and further may have any of the substituents recited above, such as alkyl and alkoxy groups. 

Examples of the alkylcarbonyloxyethyl group mentioned above include a cyclohexylcarbonyloxyethyl group, at-bu› tylcyclohexylcarbonyloxyethyl group, and an n-butylcyclo› hexy lcarbony loxyethy 1 group. 

The aryl moieties in the groups recited above have no particular restriction, too. They may generally include aryl groups having 6 to 14 carbon atoms, such as a phenyl group, a xylyl group, a tolyl group, a cumenyl group and an anthranyl group, and further may have any of the substitu› ents recited above, such as alkyl and alkoxy groups. Examples of the aryloxyethyl group mentioned above include a phenyloxyethyl group and a cyclohexylphenyloxy› ethyl group, which may further have substituents. 

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The aralkyl groups in the groups recited above have no particular restriction, too. An example of such moieties is a benzyl group. 

An example of the aralkylcarbonyloxyethyl group men- tioned above is a benzylcarbonyloxyethyl group, which may further have a substituent. 

Examples of an aralkyl group represented by each of L$_{1 }$ to L$_{4}$ , Zand Win formulae (I) and (II) include aralkyl groups having 7 to 15 carbon atoms, such as a benzyl group and a phenetyl group. These groups each may further have a substituent. 

Suitable examples of a substituent the aralkyl group may have include an alkoxy group, a hydroxyl group, a halogen atom, a nitro group, an acyl group, an acylamino group, a sulfonylamino group, an alkylthio group, an arylthio group and an aralkylthio group. Examples of an aralkyl group having a substituent include an alkoxybenzyl group, a hydroxybenzyl group and a phenylthiophenetyl group. The number of carbon atoms contained in a substituent the aralkyl group of L$_{1 }$ to L$_{4}$ , Z or W can have is preferably 12 or below. 

Examples of a 5- or 6-membered ring formed by com› bining Z and L$_{1 }$ or by combining W and L$_{4 }$ include a tetrahydropyran ring and a tetrahydrofuran ring. 

In the acid-decomposable polymer (a) used in the inven› tion, the groups Z and W represent are required to be different from each other. 

In the invention, it is preferable that the group represented by W is a group having an alicyclic radical or an aromatic group. In such a case, the group represented by Z is preferably a straight-chain or branched alkyl group. When W and Z represent those groups, the invention can achieve more marked effects. 

Suitable examples of the foregoing alicyclic group include those containing 5 to 12 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group and a cyclodecanyl group. Suitable examples of the foregoing aromatic group include those containing 6 to 16 carbon atoms, such as a phenyl group and a naphthyl group. These aromatic groups each may further have a substituent, with examples includ- ing a methylphenyl group and an ethylphenyl group. Each of those alicyclic groups or aromatic radicals may be all that constitute the group of W, or may be combined with an alkylene group or another linkage group to form the group ofW. 

Suitable examples of an alicyclic- or aromatic-containing group represented by W include a phenoxyethyl group, a cyclohexylphenoxyethyl group, a cyclohexylthioethyl group, a t-butylcyclohexylcarbonyloxyethyl group, an n-bu› tylcyclohexylcarbonyloxyethyl group, a cyclohexanone-4- yl-phenoxyethyl group, a cyclohexyl group, a cyclohexyl› ethyl group, a phenetyl group and a benzyl group. 

Suitable examples of a straight-chain or branched alkyl group represented by Z include an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an i-butyl group and at-butyl group. 

It is also admitted that edge roughness can be improved by introducing a bulky group, such as a phenyl or cyclohexyl group, to the terminal of a substituted alkyl group or a substituted aralkyl group as mentioned above. 

In the acid-decomposable polymer (a), it is preferable that the repeating units represented by formula (I) contain 5 to 60 mole % (preferably 5 to 30 mole % ) based on the total repeating units, the repeating units represented by formula (II) contain 5 to 60 mole % (preferably 5 to 30 mole % ) based on the total repeating units and the repeating units 

