TWI794304B

Provided are: a compound which can be used suitably as a photodegradable base in a resist composition that has good sensitivity to an active energy, has excellent resolution in lithography and enables the reduction in line width roughness (LWR) in a fine pattern; and a resist composition prepared using the compound. A photo-acid generator containing an onium salt compound represented by formula (1). (In formula (1), R1 and R2 independently represent any one selected from the group consisting of a hydrogen atom, a linear, branched or cyclic alkyl group which has 1 to 30 carbon atoms and may have a substituent, a linear, branched or cyclic alkenyl group which has 5 to 30 carbon atoms and may have a substituent, an aryl group which has 5 to 30 carbon atoms and may have a substituent, and a heteroaryl group which has 3 to 30 carbon atoms and may have a substituent, wherein at least one of R1 and R2 is not a hydrogen atom, a methylene group in at least one of R1 and R2 may be substituted by a bivalent hetero-atom-