Salt and photoresist composition containing the same

A salt represented by the formula (a):

• wherein Q1 and Q2 each independently represent a fluorine atom or a C1-C4 perfluoroalkyl group,
• X1 represents a single bond or —(CH2)k—, and one or more —CH2— in —(CH2)k— can be replaced by —O— or —CO— and one or more hydrogen atoms in —(CH2)k— can be replaced by a C1-C12 aliphatic hydrocarbon group, and k represents an integer of 1 to 18,
• X2 represents a single bond, a C1-C12 divalent aliphatic hydrocarbon group, a C3-C12 divalent alicyclic hydrocarbon group or a C4-C12 divalent group formed by combining a divalent aliphatic hydrocarbon group with a divalent alicyclic hydrocarbon group, and one or more —CH2— in the aliphatic hydrocarbon group can be replaced by —O— or —CO— and one or more hydrogen atoms in the aliphatic hydrocarbon group and the alicyclic hydrocarbon group can be replaced by a fluorine atom, a hydroxyl group, a C3-C36 alicyclic hydrocarbon group or a C2-C4 acyl group,
• Y1 represents a C3-C36 alicyclic hydrocarbon group, and one or more —CH2— in the alicyclic hydrocarbon group can be replaced by —O— or —CO—, and one or more hydrogen atoms in the alicyclic hydrocarbon group can be replaced by a fluorine atom, a C1-C12 aliphatic hydrocarbon group, a C3-C12 alicyclic hydrocarbon group or a C2-C4 acyl group, with the proviso that —X2—Y1 group has one or more fluorine atoms, and
• Z+ represents an organic counter cation.