US 2007/0072121 Al  9  Mar. 29, 2007  [0078]  In the acid-stable group represented by W, the alkyl  group is preferably an alkyl group having a carbon number  of 1 to 4, such as methyl group, ethyl group, propyl group,  n-butyl group, sec-butyl group and tert-butyl group; the  cycloalkyl group is preferably a cycloalkyl group having a  carbon number of 3 to 10, such as cyclopropyl group,  cyclobutyl group, cyclohexyl group and adamantyl group;  the alkenyl group is preferably an alkenyl group having a  carbon number of 2 to 4, such as vinyl group, propenyl  group, ally! group and butenyl group; the alkenyl group is  preferably an alkenyl group having a carbon number of 2 to  4, such as vinyl group, propenyl group, ally! group and  butenyl group; and the aryl group is preferably an aryl group  having a carbon number of 6 to 14, such as phenyl group,  xylyl group, toluyl group, cumenyl group, naphthyl group  and anthracenyl group. W may be present at any position on  the benzene ring but is preferably present at the meta› position or para-position, more preferably at the para-posi› tion, of the styrene skeleton.  [0079]  Specific examples of the repeating unit represented  by formula (A4) are set forth below, but the present inven› tion is not limited thereto.  [0080]  The resin (A-1) or (A-2) is a resin of which  solubility in an alkali developer increases under the action of  an acid (acid-decomposable resin), and contains a group  capable of decomposing under the action of an acid to  produce an alkali-soluble group (acid-decomposable group),  in an arbitrary repeating unit.  [0081]  As described above, the acid-decomposable group  may be contained in the repeating unit represented by  formula  (Ia), (lb) or (A2) or in other repeating unit.  [0082]  Examples of the acid-decomposable group include,  in addition to those described above, a group represented by  ----C(=)-X1-Ro.  [0083]  In the formula above, R$_{0 }$ represents, for example, a  tertiary alkyl group such as tert-butyl group and tert-amyl  group, a 1-alkoxyethyl group such as isobornyl group,  1-ethoxyethyl group, 1-butoxyethyl group, 1-isobutoxyethyl  group and 1-cyclohexyloxyethyl group, an alkoxymethyl  group such as 1-methoxymethyl group and 1-ethoxymethyl  group, a 3-oxoalkyl group, a tetrahydropyranyl group, a  tetrahydrofuranyl group, a trialkylsilyl ester group, a 3-oxo› cyclohexyl ester group, a 2-methyl-2-adamantyl group or a  mevalonic lactone group. X$_{1 }$ represents an oxygen atom, a  sulfur atom, -NH-, -NHSO$_{2}$----or -NHSO$_{2}$NH-.  [0084]  The content of the repeating unit represented by  formula  (Ia) or (lb) in the resin (A-1) or (A-2) is preferably  from 10 to 60 mo!%, more preferably from 15 to 50 mo!%,  still more preferably from 20 to 40 mo! %, based on all  repeating units.  [0085]  The content of the repeating unit represented by  formula (Al) in the resin (A-1) is preferably from 40 to 90  mo! %, more preferably from 50 to 85 mo! %, still more  preferably from 55 to 80 mo!%, based on all repeating units.  [0086]  The content of the repeating unit represented by  formula (A2) in the resin (A-2) is preferably from 5 to 60  mo! %, more preferably from 10 to 50 mo! %, still more  preferably from 20 to 40 mo!%, based on all repeating units.  [0087]  The resins (A-1) and (A-2) each may further con› tain a repeating unit represented by formula (4), and this is  preferred from the standpoint of, for example, enhancing the  film quality or suppressing the film loss in the unexposed  area. The content of the repeating unit represented by  formula (4) is preferably from 0 to 50 mo! %, more  preferably from 0 to 40 mo! %, still more preferably from 0  to 30 mo! %, based on all repeating units in each resin.  [0088]  Also, ineach of the resins (A-1) and (A-2), other  appropriate polymerizable monomer may be copolymerized  to introduce an alkali-soluble group such as phenolic  hydroxyl group or carboxyl group for maintaining good  developability with an alkali developer, or other hydropho- ---f CH2 ;::- UCN  -continued 