6  US 7,232,640 Bl  5  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  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.  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 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 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.  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 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.  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.  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.  -continued  0  (III)  OH 