wherein RA is each independently hydrogen or methyl, Z 1 is a single bond, phenylene group, ---O-Z 12 - or -C(=0)-Z 11 -Z 12 -, Z 11 is ---0- or -NH› Z12 is a C 1 -C 6 straight, branched or cyclic alkylen~ group, C$_{2}$-C$_{6 }$ straight, branched or cyclic alkenylene group or phenylene group, which may contain a carbonyl, ester, ether or hydroxy moiety, 21 28 

R to R are each independently a C 1 -C$_{12 }$ straight, branched or cyclic alkyl group which may contain a carbonyl, ester or ether moiety, or a CcC$_{12 }$ aryl group or C$_{7}$-C$_{20 }$ aralkyl group, in which at least one hydrogen may be substituted by a C$_{1 }$-C$_{10 }$ straight, branched or cyclic alkyl moiety, halogen, trifluorom› ethyl, cyano, nitro, hydroxyl, mercapto, C$_{1 }$-C$_{10 }$ straight, branched or cyclic alkoxy moiety, C$_{2}$-C$_{10 }$ straight, branched or cyclic alkoxycarbonyl moiety, or C$_{2}$-C$_{10 }$ straight, branched or cyclic acyloxy moi› ety, any two ofR 23 , R 24 and R 25 , or any two ofR 26 , R 27 and R 28 may bond together to form a ring with the sulfur atom to which they are attached, 2 21 21 

Z is a single bond, -Z -C(=0)---0-, _z _ 0- or -Z 21 -0----C(=0)-, Z 21 is a $^{C}$1-C$_{12 }$ straight, branched or cyclic alkylene group which may contain a carbonyl, ester or ether moiety, 

A is hydrogen or trifluoromethyl, 3 

Z is a single bond, methylene group, ethylene group, phenylene group, fluorinated phenylene group, -0-Z 32 -, or ----C(=0)-Z$^{31}$-Z 32 -, Z 31 is -0- or -NH-, Z 32 is a C 1 -C 6 straight, branched 

or cyclic alkylene group, phenylene, fluorinated phe› nylene or trifluoromethyl-substituted phenylene group, or C$_{2}$-C$_{6 }$ straight, branched or cyclic alk- enylene group, which may contain a carbonyl, ester, ether or hydroxyl moiety, and 

M- is a non-nucleophilic counter ion. 

13. A process for forming a pattern comprising the steps of applying the resist composition of claim 1 onto a sub› strate, baking to form a resist film, exposing the resist film to high-energy radiation, and developing the exposed film in a developer. 

14. The process of claim 13 wherein the high-energy radiation is ArF excimer laser radiation of wavelength 193 nm or KrF excimer laser radiation of wavelength 248 nm. 

15. The process of claim 13 wherein the high-energy radiation is electron beam or extreme ultraviolet radiation of wavelength 3 to 15 nm. 

16. A process for forming a pattern comprising the steps of applying the resist composition of claim 12 onto a substrate, baking to form a resist film, exposing the resist film to high-energy radiation, and developing the exposed film in a developer. 

17. The process of claim 16 wherein the high-energy radiation is ArF excimer laser radiation of wavelength 193 nm or KrF excimer laser radiation of wavelength 248 nm. 

18. The process of claim 16 wherein the high-energy radiation is electron beam or extreme ultraviolet radiation of wavelength 3 to 15 nm. 

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