Resist composition and pattern forming process

A resist composition comprising a quencher containing a sulfonium salt having the formula (A):

• wherein k, m, and n are each independently an integer of 1 to 3, p is 0 or 1, q is an integer of 0 to 4, r is an integer of 1 to 3,
• XBI is iodine or bromine,
• Ra1 is a C1-C20 (k+1)-valent aliphatic hydrocarbon group which may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate group, a halogen other than iodine, a C6-C12 aryl group, a hydroxyl group, or a carboxyl group,
• X1 is a single bond, an ether bond, an ester bond, an amide bond, a carbonyl group, or a carbonate group,
• X2 is a single bond or a C1-C20 (m+1)-valent hydrocarbon group which may contain at least one selected from an ether bond, a carbonyl group, an ester bond, an amide bond, a sultone ring, a lactam ring, a carbonate group, a halogen other than iodine, a hydroxyl group, or a carboxyl group,
• X3 is a single bond, an ether bond, or an ester bond,
• R1 is a single bond or a C1-C20 saturated hydrocarbylene group which may contain an ether bond, an ester bond, or a hydroxyl group,
• R2 is a C1-C20 hydrocarbyl group which may contain a heteroatom, two R2s may be the same or different, and may bond together to form a ring with a sulfur atom to which the two R2s are attached when r=1,
• R3 is a hydroxyl group, a carboxyl group, a nitro group, a cyano group, fluorine, chlorine, bromine, iodine, an amino group, or a C1-C20 saturated hydrocarbyl group, C1-C20 saturated hydrocarbyloxy group, C2-C20 saturated hydrocarbylcarbonyloxy group, C2-C20 saturated hydrocarbyloxycarbonyl group, or C1-C4 saturated hydrocarbylsulfonyloxy group which may contain fluorine, chlorine, bromine, iodine, a hydroxyl group, an amino group, or an ether bond, and
• Xq− is a halide ion, a sulfonic acid anion not having fluorine at an α-position, a carboxylic acid anion, or a sulfonamide anion.