Sulfonium salt-containing polymer, resist composition, patterning process, and sulfonium salt monomer and making method

A sulfonium salt having the general formula (1):

• wherein R1 is hydrogen, fluorine, methyl or trifluoromethyl, R2, R3, and R4 are each independently a substituted or unsubstituted, straight or branched C1-C10 alkyl, alkenyl or oxoalkyl group, a substituted or unsubstituted C6-C18 aryl, aralkyl or aryloxoalkyl group, or 4-fluorophenyl group, any two of R2, R3, and R4 may bond together to form a ring with the sulfur atom, with the proviso that at least one of R2, R3, and R4 is a 4-fluorophenyl group.