Resist composition and patterning process

A resist composition comprising a base polymer and a sulfonium salt having the formula (A):

• wherein R1 is a C1-C6 straight, branched or cyclic alkyl or alkoxy group, C2-C6 straight, branched or cyclic acyloxy group, or C1-C4 straight, branched or cyclic alkylsulfonyloxy group, in which at least one hydrogen may be substituted by a halogen atom, or fluorine, chlorine, bromine, amino group, nitro group, cyano group, —NR5—C(═O)—R6, or —NR5—C(═O)—O—R6, wherein R5 is hydrogen or a C1-C6 straight, branched or cyclic alkyl group, R6 is a C1-C6 straight, branched or cyclic alkyl group or C2-C8 straight, branched or cyclic alkenyl group,
• X is a single bond or a (p+1)-valent C1-C20 linking group which may contain an ether, carbonyl, ester, amide, sultone, lactam, carbonate, halogen, hydroxy or carboxy moiety,
• R2, R3 and R4 are each independently fluorine, chlorine, bromine, iodine, or a C1-C12 straight, branched or cyclic alkyl group which may contain an oxo moiety, a C2-C12 straight, branched or cyclic alkenyl group which may contain an oxo moiety, C6-C20 aryl group, C7-C12 aralkyl group or C7-C12 aryloxyalkyl group, in which at least one hydrogen may be substituted by a hydroxy, carboxy, halogen, cyano, amide, nitro, sultone, sulfone or sulfonium salt-containing moiety, or in which an ether, ester, carbonyl, carbonate or sulfonic acid ester moiety may intervene between carbon atoms, or R2 and R3 may bond together to form a ring with the sulfur atom to which they are attached,
• m is an integer of 1 to 5, n is an integer of 0 to 3, and p is an integer of 1 to 3.