The present invention relates to (A) 3,3,3-trifluoro-2-hydroxy-2-trifluoromethylpropionic acid sulfonium salt represented by the formula (1-1) (Ar 'is an aryl group, or a plurality of Ar' s may be bonded directly or through an oxygen atom, a methylene group, a sulfone group or a carbonyl group, and may form a ring containing an aromatic ring together with a sulfur atom) (B) an acid generator represented by the general formula (1-2) (Wherein R 4 is an alkyl group, an alkenyl group or an aralkyl group, R 5 is a hydrogen atom or a trifluoromethyl group, and Ar 'is the same as defined above) (C) an alkali developing solution having an acidic functional group protected by an acid labile group, which is insoluble or hardly soluble, a base resin which is soluble in an alkaline developing solution when the acid labile group is deprotected, (D) Organic solvents As an essential component, to a chemically amplified positive resist composition for ArF immersion lithography. The carboxylic acid sulfonium salt used in the resist material of the present invention has high hydrophobicity when used in a resist material and has low dissolution to immersion water, so that acid diffusion can be controlled, and thus a pattern profile of high resolution can be formed.
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