Resist composition and patterning process

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

• wherein m is an integer of 1 to 5, n is an integer of 0 to 3, m+n is 1 to 5, p is an integer of 1 to 3,
• L1 is a single bond or C1-C20 divalent linking group when p=1, or a C1-C20 tri- or tetravalent linking group when p=2 or 3, the linking group optionally containing oxygen, sulfur or nitrogen,
• Rf1 to Rf4 are each independently hydrogen, fluorine or trifluoromethyl, at least one of Rf1 to Rf4 being fluorine or trifluoromethyl, Rf1 and Rf2, taken together, may form a carbonyl group,
• R1 is hydroxyl, carboxyl, nitro, cyano, fluorine, chlorine, bromine, amino, or a C1-C20 saturated hydrocarbyl, C1-C20 saturated hydrocarbyloxy, C2-C20 saturated hydrocarbyloxycarbonyl, C2-C20 saturated hydrocarbylcarbonyloxy or C1-C4 saturated hydrocarbylsulfonyloxy group, which may contain fluorine, chlorine, bromine, hydroxyl, amino or ether bond, or —NR1A—C(═O)—R1B or —NR1A—C(═O)—O—R1B, R1A is hydrogen or a C1-C6 saturated hydrocarbyl group which may contain halogen, hydroxyl, C1-C6 saturated hydrocarbyloxy, C2-C6 saturated hydrocarbylcarbonyl or C2-C6 saturated hydrocarbylcarbonyloxy moiety, R1B is a C1-C16 aliphatic hydrocarbyl group or C6-C12 aryl group, which may contain halogen, hydroxyl, C1-C6 saturated hydrocarbyloxy, C2-C6 saturated hydrocarbylcarbonyl or C2-C6 saturated hydrocarbylcarbonyloxy moiety,
• R2 is hydrogen or C1-C4 alkyl, R2 and L1 may bond together to form a ring with the nitrogen atom to which they are attached,
• R3, R4, R5, R6, and R7 are each independently a C1-C20 hydrocarbyl group which may contain a heteroatom, R3 and R4 may bond together to form a ring with the sulfur atom to which they are attached.