Resist composition and patterning process

A resist composition comprising a base polymer and a sulfonium salt having the formula (A-1) and/or an iodonium salt having the formula (A-2):

• wherein R1 is a hydroxyl group, carboxyl group, C1-C6 straight, branched or cyclic alkyl or alkoxy group, C2-C6 straight, branched or cyclic acyloxy group, fluorine, chlorine, bromine, amino, —NR8—C(═O)—R9, or —NR8—C(═O)—O—R9, R8 is hydrogen or a C1-C6 straight, branched or cyclic alkyl group, R9 is a C1-C6 straight, branched or cyclic alkyl group or C2-C8 straight, branched or cyclic alkenyl group;
• R2 is a C2-C12 straight, branched or cyclic alkylene group or C6-C10 arylene group, at least one hydrogen in the alkylene group being optionally substituted by a halogen other than fluorine, at least one hydrogen in the arylene group being optionally substituted by a C1-C10 straight, branched or cyclic alkyl or alkoxy moiety, halogen other than fluorine, or hydroxyl moiety,
• R3, R4 and R5 are each independently fluorine, chlorine, bromine, iodine, C1-C12 straight, branched or cyclic alkyl group, C2-C12 straight, branched or cyclic alkenyl group, C6-C20 aryl group, or C7-C12 aralkyl or aryloxoalkyl group, at least one hydrogen in the foregoing groups being optionally substituted by a hydroxyl, carboxyl, halogen, oxo, cyano, amide, nitro, sultone, sulfone or sulfonium salt-containing moiety, or at least one carbon in the foregoing groups being optionally substituted by an ether, ester, carbonyl, carbonate or sulfonate moiety, or R3 and R4 may bond together to form a ring with the sulfur atom to which they are attached,
• R6 and R7 are each independently trifluoromethyl, a C6-C10 aryl group, C2-C6 straight, branched or cyclic alkenyl group, or C2-C6 straight, branched or cyclic alkynyl group, at least one hydrogen in the foregoing groups being optionally substituted by a halogen, trifluoromethyl, C1-C10 straight, branched or cyclic alkyl or alkoxy, hydroxyl, carboxyl, C2-C10 straight, branched or cyclic alkoxycarbonyl, nitro or cyano moiety,
• X1 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, hydroxyl or carboxyl moiety,
• X2 is an ether group or —NR10—, R10 is hydrogen or C1-C4 straight or branched alkyl group,
• 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.