Chemically amplified resist composition and patterning process

A chemically amplified resist composition comprising, a quencher containing an iodonium iodide, and an acid generator,

• wherein the acid generator also functions as a base polymer, and
• the acid generator is a polymer comprising recurring units of at least one type selected from recurring units having the formulae (f1) to (f3):
• wherein RA is each independently hydrogen or methyl,
• Z1 is a single bond, phenylene, —O—Z11—, or —C(═O)—Z12—Z11—, Z11 is a C1-C6 straight, branched or cyclic alkylene group or C2-C6 straight, branched or cyclic alkenylene group which may contain a carbonyl, ester, ether or hydroxyl moiety, or phenylene group, Z12 is —O— or —NH—,
• R51, R52, R53, R54, R55, R56, R57, and R58 are each independently a C1-C12 straight, branched, or cyclic alkyl group which may contain a carbonyl ester or ether moiety or a C6-C12 aryl, C7-C20 aralkyl, or mercaptophenyl group,
• Z2 is a single bond, —Z21—C(═O)—O—, —Z21—O—, or —Z21—O—C(═O)—, Z21 is a C1-C12 straight, branched or cyclic alkylene group which may contain a carbonyl, ester or ether moiety,
• Z3 is a single bond, methylene, ethylene, phenylene, fluorinated phenylene, —O—Z31—, or —C(═O)—Z32—Z31, Z31 is a C1-C6 straight, branched or cyclic alkylene group or C2-C6 straight, branched or cyclic alkenylene group which may contain a carbonyl, ester, ether or hydroxyl moiety, or a phenylene, fluorinated phenylene or trifluoromethyl-substituted phenylene group, Z32 is —O— or —NH—,
• A1 is hydrogen or trifluoromethyl, and M− is a non-nucleophilic counter ion.