Resist composition and patterning process using the same

A resist composition comprising a polymer in which:

• a sulfonium salt having a polymerizable unsaturated double bond,
• a (meth)acrylate having a lactone or a hydroxyl group as adhesion group, and
• a (meth)acrylate having an ester substituted with an acid labile group are copolymerized;
• wherein the repeating unit formed from the sulfonium salt having a polymerizable unsaturated bond is represented by the following general formula (1)
• where:
• R1 represents a hydrogen atom or a methyl group,
• R2 represents any one of:
• —O—R6—,
• —C(═O)—X1—R6—,
• —C(═O)—O—C2H4—O—Y1—,
• —C(═O)—O-Z1-C(═O)—CH2—,
• —Z1—C(═O)—CH2—,
• —C(═O)—O—Z1—CH2—,
• —C(═O)—O—CH2—C(═O)—O—Z1-, and
• —C(═O)—O—C2H4—C(═O)—O—Z1-,
• where:
• X1 represents an oxygen atom or NH,
• R6 represents a linear, branched or cyclic alkylene group having 1-6 carbon atoms or a phenylene group which may contain a carbonyl group, an ester group or an ether group,
• Y1 represents any one of a phenylene group, a naphthylene group, and an anthrylene group, and
• Z1 represents a phenylene group,
• R3 and R4 each independently represents:
• a linear, branched or cyclic alkyl group having 1-12 carbon atoms which may contain a carbonyl group, an ester group or an ether group,
• an aryl group having 6-12 carbon atoms,
• an aralkyl group having 7-20 carbon atoms or a thiophenyl group, or
• R3 and R4 may bond each other to form a ring, and
• R5 represents a perfluoro-4-ethylcyclohexyl group.