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the base polymer because it is free of fluorine at a-position of sulfa group, but has two trifluoromethyl groups at ~-po› sition. Thus the compound is a useful PAG. 

[0113] Further, compounds having the formula (2) are useful as the PAG. 

[0114] 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. LA is a single bond or 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. 

[0115] The monovalent hydrocarbon groups may be straight, branched or cyclic and include straight or branched alkyl groups such as methyl, ethyl, propyl, isopropyl, n-bu› tyl, s-butyl, t-butyl, n-pentyl, t-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, and 2-ethylhexyl; monovalent saturated cyclic hydrocarbon groups such as cyclopentyl, cyclohexyl, cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl, cyclohexylethyl, cyclohexylbutyl, nor› bomyl, oxanorbomyl, tricyclo[5.2.l.0 2 • $^{6}$]decanyl, and ada› mantyl; and aryl groups such as phenyl, naphthyl and anthracenyl. Also included are the foregoing groups in which at least one hydrogen is substituted by a heteroatom such as oxygen, sulfur, nitrogen or halogen, or in which at least one carbon is substituted 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, carboxylic acid anhydride or haloalkyl moiety. 

[0116] The divalent hydrocarbon groups may be straight, branched or cyclic, and examples thereof include linear or branched alkane diyl 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-diy 1, undecane-1, 11-diy 1, dodecane-1, 12-diy 1, tridecane-1, 13-diyl, tetradecane-1, 14-diyl, pentadecane-1, 15-diy 1, hexadecane-1, 16-diy 1, heptadecane-1, 17 -diyl; satu› rated cyclic divalent hydrocarbon groups such as cyclopen› tanediyl, cyclohexanediyl, norbomanediyl, and adamantanediyl; and unsaturated cyclic divalent hydrocar› bon groups such as phenylene and naphthylene. Also included are the foregoing groups in which at least one hydrogen atom is substituted by an alkyl group such as methyl, ethyl, propyl, n-butyl or t-butyl, or in which at least one hydrogen atom is substituted by a moiety containing a heteroatom such as oxygen, sulfur, nitrogen or halogen, or in which at least one carbon atom is substituted 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, 

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lactone ring, sultone ring, carboxylic acid anhydride or haloalkyl moiety. Suitable heteroatoms include oxygen, nitrogen, sulfur and halogen, with oxygen being preferred. 

[0117] Of the PAGs having formula (2), those having formula (2’) are preferred. 

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[0118] In formula (2’), LA is as defined above. R is hydro› gen 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 het› eroatom. The monovalent hydrocarbon groups may be straight, branched or cyclic, and examples thereof are as exemplified above for R 105 . The subscripts x and y each are an integer of 0 to 5, and z is an integer of 0 to 4. 

[0119] Examples of the PAG having formula (2) are shown below, but not limited thereto. Herein R is as defined above. 

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