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[0129] The compound having the anion of formula (ID) has a sufficient acid strength to cleave acid labile groups in the base polymer because it is free of fluorine at a-position of sulfa group, but has two trifluoromethyl groups at 3-po› sition. Thus the compound is a useful PAG. 

[0130] A compound having the formula (2) is also a useful PAG. 

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[0131] In formula (2), R 201 and R 202 are each indepen› dently a C$_{1 }$-C$_{30 }$monovalent hydrocarbon group which may contain a heteroatom. R$^{203 }$is a C$_{1}$-C$_{30 }$divalent hydrocarbon group which may contain a heteroatom. Any two of R 201 , R$^{202 }$and R$^{203 }$may bond together to form a ring with the sulfur atom to which they are attached. L is a single bond, ether bond or a C$_{1 }$-C$_{20 }$ divalent hydrocarbon group which may contain a heteroatom. XA, XB, Xe and xn are each independently hydrogen, fluorine or trifluoromethyl, with the proviso that at least one ofXA, XB, Xe and xn is fluorine or trifluoromethyl, and k is an integer of Oto 3. 

[0132] The monovalent hydrocarbon group may be straight, branched or cyclic. Examples thereof include straight or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, tert-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, 2-ethylhexyl; monovalent saturated cyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentyl› ethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, norbormyl, oxanorbornyl, tricyclo[5.2.1. 0 2 • $^{6}$]decanyl, adamantyl; aryl groups such as phenyl, naph› thyl and anthracenyl. Also included are the foregoing groups in which some hydrogen is substituted by a moiety contain› ing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or in which some carbon is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxyl, cyano, carbonyl, ether bond, ester bond, sulfonic acid ester bond, carbonate bond, lactone ring, sultone ring, carboxylic acid anhydride or haloalkyl moiety. 

[0133] The divalent hydrocarbon group may be straight, branched or cyclic. Examples thereof include straight or branched alkanediyl groups such as methylene, ethylene, propane-1,3-diy 1, butane-1,4-diy 1, pentane-1, 5-diy 1, hexane- 1,6-diy l, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, 

decane-1, 10-diyl, undecane-1, 11-diyl, dodecane-1, 12-diyl, tridecane-1, 13-diyl, tetradecane-1, 14-diyl, pentadecane-1, 15-diyl, hexadecane-1,16-diyl, heptadecane-1,17-diyl; diva› lent saturated cyclic hydrocarbon groups such as cyclopen› tanediyl, cyclohexanediyl, norbornanediyl, and adamantanediyl; and divalent unsaturated cyclic hydrocar› bon groups such as phenylene and naphthylene. Also included are the foregoing groups in which some hydrogen is substituted by an alkyl group such as methyl, ethyl, propyl, n-butyl or tert-butyl, or in which some hydrogen is substituted by a moiety containing a heteroatom such as oxygen, sulfiur, nitrogen or halogen, or in which some carbon is replaced by a moiety containing a heteroatom such as oxygen, sulfur or nitrogen, so that the group may contain a hydroxyl, cyano, carbonyl, ether bond, ester bond, sulfonic acid ester bond, carbonate, lactone ring, sultone ring, car› boxylic acid anhydride or haloalkyl moiety. The preferred heteroatom is oxygen. 

[0134] Of the PAGs having formula (2), those having formula (2’) are preferred. 

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[0135] In formula (2’), L is as defined above. "A" is hydrogen or trifluoromethyl, preferably trifluoromethyl. R 301 , R $^{302 }$and R$^{303 }$are each independently hydrogen or a C$_{1 }$-C$_{20 }$monovalent hydrocarbon group which may contain a heteroatom. The monovalent hydrocarbon group may be straight, branched or cyclic and examples thereof are as exemplified above for R 107 . The subscripts x and y each are an integer of 0 to 5, and z is an integer of 0 to 4. 

[0136] Examples of the PAG having formula (2) are shown below, but not limited thereto. Herein "A" is as defined above. 

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