52  US 8,637,222 B2  51  The aryl group, alkyl group and cycloalkyl group ofR$_{204 }$to  R$_{207 }$ may have a substituent. Examples of the substituent  include those of the substituent which the aryl group, alkyl  group and cycloalkyl group ofR$_{201 }$to R$_{203 }$in the compound  (ZI)  may have.  z- represents a non-nucleophilic anion, and examples  thereof are the same as those of the non-nucleophilic anion of  z- in formula  (ZI).  The acid generator further includes compounds repre› sented by the following formulae  (ZIV), (ZV)  and  (ZVI):  In formula (Al), each ofR 1 a to R 13 a independently repre› sents a hydrogen atom, a halogen atom, a nitro group or an  organic group.  From one to three members out ofR 1 a to R 13 a are prefer› ably not a hydrogen atom, and it is more preferred that at least  any one of  R 9 a  to R  13$_{a }$ is not a hydrogen atom.  Za represents a single bond or a divalent linking group.  x- has the same meaning as z- in formula  (ZI).  Specific examples of R 1 a to R 13 a when these are not a  hydrogen atom include a halogen atom, a nitro group, a linear,  branched or cyclic alkyl group, an alkenyl group, an alkynyl  group, an aryl group, a heterocyclic group, a cyano group, a  carboxyl group, an alkoxy group, an aryloxy group, a silyloxy  group, a heterocyclic oxy group, an acyloxy group, a carbam› oyloxy group, an alkoxycarbonyloxy group, an aryloxycar- bonyloxy group, an amino group (including an anilino  group), an acylamino group, an aminocarbonylamino group,  an alkoxycarbonylamino group, an aryloxycarbonylamino  group, a sulfamoylamino group, an alkylsulfonylamino  group, an arylsulfonylamino group, an alkylthio group, an  arylthio group, a heterocyclic thio group, an alkylsulfinyl  group, an arylsulfinyl group, an alkylsulfonyl group, an aryl› sulfonyl group, an acyl group, an aryloxycarbonyl group, an  alkoxycarbonyl group, a carbamoyl group, an arylazo group,  a heterocyclic azo group, a phosphinylamino group, a silyl  grouR, a ureido group, and other known organic groups.  R  a  to R  13$_{a }$ are, when these are not a hydrogen atom,  preferably a linear, branched or cyclic alkyl group substituted  by a hydroxyl group.  Examples of the divalent linking group of Za include an  alkylene group, anarylene group, a carbonyl group, a sulfonyl  group, a carbonyloxy group, a carbonylamino group, a sulfo› nylamide group, -0-, -S-, an amino group, a disulfide  group,  -(CH$_{2}$)n-CO-,  -(CH$_{2}$)n-SO$_{2}$-,  -CH=CH-, an aminocarbonylamino group and an ami- nosulfonylamino group (n is an integer of 1 to 3).  Incidentally, preferred examples of the structure where at  least one ofR$_{20}$ i,  R$_{202 }$and R$_{203 }$is not an aryl group include a  cation structure such as compounds described in paragraphs  0046 and 0047 ofJP-A-2004-233661 and paragraphs 0040 to  0046 of JP-A-2003-35948, compounds illustrated as formu- lae (I-1) to (1-70) in U.S. Patent Application Publication No.  2003/0224288Al, and compounds illustrated as formulae  (IA-1) to (IA-54) and formulae (IB-1) to (IB-24) in U.S.  Patent Application Publication No. 2003/0077540A 1.  In formulae  (ZII)  and  (ZIII),  each ofR$_{204 }$to R$_{207 }$indepen- dently represents an aryl group, an alkyl group or a cycloalkyl  group.  The aryl group, alkyl group and cycloalkyl group ofR$_{204 }$to  R$_{207 }$ are the same as the aryl group, alkyl group and  cycloalkyl group ofR$_{201 }$to R$_{203 }$in the compound (ZI).  Out of the acid generators, particularly preferred examples  are set forth below.  The alkylene group of A includes an alkylene group having  a carbon number of 1 to 12 (e.g., methylene, ethylene, pro› pylene, isopropylene, butylene, isobutylene ), the alkenylene  group of A includes an alkenylene group having a carbon  number of 2 to 12 (e.g., ethynylene, propenylene, bute› nylene ), and the arylene group of A includes an arylene group  having a carbon number of 6 to 10 ( e.g., phenylene, tolylene,  naphthylene ).  Specific examples of the alkyl group and cycloalkyl group  ofR$_{208}$, R$_{209 }$and R$_{210 }$are the same as specific examples of the  alkyl group and cycloalkyl group ofR$_{201}$ , R $_{202 }$and R$_{203 }$ in  formula  (ZI).  Specific examples of the aryl group of Ar$_{3}$ ,  Ar$_{4}$ ,  R$_{208}$, R 209  and R$_{210 }$are the same as specific examples of the aryl group  ofR$_{20}$ i,  R$_{202 }$and R$_{203 }$in formula  (ZI).  A represents an alkylene group, an alkenylene group or an  arylene group.  Each of R$_{208}$ , R $_{209 }$and R$_{210 }$independently represents an  alkyl group, a cycloalkyl group or an aryl group.  In formulae  (ZIV)  to  (ZVI),  each ofAr$_{3 }$ andAr$_{4 }$ indepen› dently represents an aryl group.  (z4)  (z2)  (zl)  (z3)  (ZVI)  (ZV)  (ZIV) 