16. A resist composition comprising a base polymer and a sulfonium or iodonium salt having the formula (A):wherein the circle RA is a C3-C12 cyclic hydrocarbon group which may contain an ether, ester, thiol, sulfone moiety or double bond and may be a bridged ring, or a C6-C10 aryl group,R1 is hydrogen or a straight, branched or cyclic C1-C6 alkyl group,
m is an integer of 0 to 5,
R2 is selected from the group consisting of straight, branched or cyclic C1-C6 alkyl, acetyl, methoxycarbonyl, ethoxycarbonyl, n-propyloxycarbonyl, isopropyloxycarbonyl, t-butoxycarbonyl, t-pentyloxycarbonyl, methylcyclopentyloxycarbonyl, ethylcyclopentyloxycarbonyl, methylcyclohexyloxycarbonyl, ethylcyclohexyloxycarbonyl, 9-fluorenylmethyloxycarbonyl, allyloxycarbonyl, phenyl, benzyl, naphthyl, naphthylmethyl, methoxymethyl, ethoxymethyl, propoxymethyl, and butoxymethyl,
R3 is a straight, branched or cyclic C1-C24 alkylene group which may contain a hydroxyl, alkoxy, ether, ester, sulfonic acid ester, cyano moiety, halogen atom, double bond, triple bond or aromatic moiety, with the proviso that the ?-carbon attached to SO3? in formula (A) is not substituted with fluorine,
A+ is a sulfonium cation having the formula (B) or iodonium cation having the formula (C):
wherein R4, R5 and R6 are each independently a straight, branched or cyclic C1-C12 alkyl or oxoalkyl group, a straight, branched or cyclic C2-C12 alkenyl or oxoalkenyl group, C6-C20 aryl group, or C7-C12 aralkyl or aryloxoalkyl group, in which at least one hydrogen may be substituted by a substituent containing an ether, ester, carbonyl, carbonate, hydroxyl, carboxyl, halogen, cyano, amide, nitro, sultone, sulfonic acid ester, sulfone, thiol moiety or sulfonium salt,R7 and R8 are each independently a C6-C20 aryl group in which at least one hydrogen may be substituted by a straight, branched or cyclic C1-C10 alkyl or alkoxy moiety.