Salt and photoresist composition containing the same

A photoresist composition comprising a polymer comprising a structureal unit derived from a salt represented by the formula (I-Pa):

• wherein XPa represents a single bond or a C1-C4 alkylene group,
• RPa represents a single bond, a C4-C36 divalent alicyclic hydrocarbon group or a C6-C36 divalent aromatic hydrocarbon group, and one or more methylene groups in the divalent alicyclic hydrocarbon group can be replaced by —O— or —CO—,
• YPa represents a polymerizable group, and
• ZPa+ represents an organic cation, and
• a salt represented by the formula (I):
• wherein Q1 and Q2 each independently represent a fluorine atom or a C1-C4 perfluoroalkyl group,
• X1 represents a single bond or a C1-C17 saturated hydrocarbon group which can have one or more substituents, and one or more methylene groups in the saturated hydrocarbon group can be replaced by —O— or —CO—,
• Y1 represents a C1-C36 aliphatic hydrocarbon group, a C3-C36 alicyclic hydrocarbon group or a C6-C24 aromatic hydrocarbon group, and the aliphatic hydrocarbon group, the alicyclic hydrocarbon group and the aromatic hydrocarbon group can have one or more substituents, and one or more methylene groups in the aliphatic hydrocarbon group and the alicyclic hydrocarbon group can be replaced by —O— or —CO—,
• Z+ represents an organic cation.