Abstract: A photoresist composition containing an alkylsulfonium salt compound represented by the following general formula (I): ##STR1## Wherein R.sup.1 and R.sup.2 may be the same or different, each being a linear, branched or cyclic C.sub.1 to C.sub.8 alkyl radical, R.sup.3 is a linear, branched or cyclic C.sub.1 to C.sub.8 alkyl radical, a C.sub.5 to C.sub.7 2-oxocycloalkyl radical, or a linear or branched C.sub.3 to C.sub.8 2-oxoalkyl radical, and Y.sup.- represents a counter ion. The photoresist composition has high transparency to deep U.V. light having wavelengths of 220 nm or less and is capable of forming good fine patterns with high sensitivity, thus being useful as chemically amplified type resist which is exposed to the deep U.V. light from an ArF excimer laser.

Abstract: There is provided an highpolymer of the formula: ##STR1## where at least one of R.sup.1 and R.sup.2 is either an alkyl group having 1 and 3 carbons atoms or an alkoxy group having 1 to 3 carbon atoms and the other is hydrogen, R.sup.3 is either a phenyl group or an alkyl group having 1 to 3 carbon atoms, x satisfies the condition that 0<x.ltoreq.1, n is a positive integer in the range of from 5 to 700, Y.sup.- is a non-nucleophilic paired ion.