Sulfonium compound

A sulfonium compound represented by the formula (I):

• wherein Q1 and Q2 each independently represent a fluorine atom or a C1-C6 perfluoroalkyl group, and A+ represents an organic counter ion;
• wherein the organic counter ion is at least one cation selected from a cation represented by the formula (IIa):
• wherein P1, P2 and P3 each independently represent a C1-C30 alkyl group which may be substituted with at least one selected from a hydroxyl group, a C3-C12 cyclic hydrocarbon group and a C1-C12 alkoxy group, or a C3-C30 cyclic hydrocarbon group which may be substituted with at least one selected from a hydroxyl group and a C1-C12 alkoxy group, a cation represented by the formula (IIb):
• wherein P4 and P5 each independently represent a hydrogen atom, a hydroxyl group, a C1-C12 alkyl group or a C1-C12 alkoxy group, a cation represented by the formula (IIc):
• wherein P6 and P7 each independently represent a C1-C12 alkyl group or a C3-C12 cycloalkyl group, or P6 and P7 are bonded together to form a C3-C12 divalent acyclic hydrocarbon group which forms a ring together with the adjacent S+, and at least one —CH2— in the divalent acyclic hydrocarbon group may be replaced with —CO—, —O— or —S—, P8 represents a hydrogen atom, P9 represents a C1-C12 alkyl group, a C3-C12 cycloalkyl group or an aromatic group which may be substituted, or P8 and P9 are bonded together to form a divalent acyclic hydrocarbon group which forms a 2-oxocycloalkyl group together with the adjacent —CHCO—, and at least one —CH2— in the divalent acyclic hydrocarbon group may be replaced with —CO—, —O— or —S—, and a cation represented by the formula (IId):
• wherein P10, P11, P12, P13, P14, P15, P16, P17, P18, P19,P20and P21each independently represent a hydrogen atom, a hydroxyl group, a C1-C12 alkyl group or a C1-C12 alkoxy group, B represents a sulfur or oxygen atom and k represents 0 or 1.