Photoresist composition

A photoresist composition comprising

• a resin which comprises a structural unit derived from a compound represented by the formula (a1-1):
• wherein Ra4 represents a hydrogen atom or a methyl group, Ra6 represents a C1-C8 aliphatic hydrocarbon group or a C3-C10 saturated cyclic hydrocarbon group, La1 represents *—O— or *—O—(CH2)k1—CO—O— in which * represents a binding position to —CO—, and k1 represents an integer of 1 to 7, and m1 represents an integer of 0 to 14;
• a structural unit derived from a compound represented by the formula (a2-0):
• wherein R8 represents a hydrogen atom, a halogen atom, a C1-C6 alkyl group or a C1-C6 halogenated alkyl group, R9 is independently in each occurrence a halogen atom, a hydroxyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C4 acyl group, a C2-C4 acyloxy group, an acryloyl group or a methacryloyl group, ma represents an integer of 0 to 4, and a structural unit derived from a compound selected from the group consisting of styrene, a compound having no acid-labile group but having a lactone ring and a compound represented by formula (a2-1):
• wherein Ra14 represents a hydrogen atom or a methyl group, Ra15 and Ra16 each independently represent a hydrogen atom, a methyl group or a hydroxyl group, La3 represents *—O— or *—O—(CH2)k2—CO—O— in which * represents a binding position to —CO—, and k2 represents an integer of 1 to 7, and o1 represents an integer of 0 to 10,
• which resin is insoluble or poorly soluble in an alkali aqueous solution but becomes soluble in an alkali aqueous solution by the action of an acid;
• no other acid generator than an acid generator represented by formula (B1)
• in which Q1 and Q2 each independently represent a fluorine atom or a C1-C6 perfluoroalkyl group;
• wherein Lb1 represents *—CO—O-Lb2-, *—CO—O-Lb4-CO—O-Lb3, *-LB7-O-Lb6-, *—CO—O-Lb8-O—, or *—CO—O-Lb10-O-Lb9-CO—O— in which Lb2 represents a single bond or a C1-C15 alkanediyl group, Lb3 represents a single bond or a C1-C12 alkanediyl group, Lb4 represents a single bond or a C1-C13 alkanediyl group, with proviso that total carbon number of Lb3 and Lb4 is 1 to 13, Lb6 represents a C1-C15 alkanediyl group, Lb7 represents a C1-C15 alkanediyl group, with proviso that total carbon number of Lb6 and Lb7 is 1 to 16, Lb8 represents a C1-C14 alkanediyl group, Lb9 represents a C1-C11 alkanediyl group, Lb10 represents a C1-C11 alkanediyl group, with proviso that total carbon number of Lb9 and Lb10 is 1 to 12, and * represents a binding position to —C(Q1)(Q2)-,
• wherein Y represents a C3-C18 saturated cyclic hydrocarbon group which can have one or more substituents, and one or more methylene groups in the saturated cyclic hydrocarbon group can be replaced by —O—,—CO—, or —SO2— and
• wherein Z+ represents an organic cation represented by formula (b2-1):
• where Rb4, Rb5 and Rb6 each independently represent a C1-C30 aliphatic hydrocarbon group which can have one or more substituents selected from the group consisting of a hydroxyl group, a C1-C12 alkoxy group and a C6-C18 aromatic hydrocarbon group, a C3-C36 saturated cyclic hydrocarbon group which can have one or more substituents selected from the group consisting of a halogen atom, a C2-C4 acyl group and a glycidyloxy group, or a C6-C18 aromatic hydrocarbon group which can have one or more substituents selected from the group consisting of a halogen atom, a hydroxyl group, a C1-C36 aliphatic hydrocarbon group, a C3-C36 saturated cyclic hydrocarbon group or a C1-C12 alkoxy group;
• and
• a compound represented by the formula (I′):
• wherein the cation part represents a cation by any one of the following formulae:
• and the anion part represents an anion represented by any one of the following formulae