93  US 10,606,172 B2  94  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,  R 21  to R 28  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,  Z 2  is a single bond, -Z 21 -C(=0)---0-,  _z 21 _  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,  Z 3  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.  *  *  *  *  * 