Photoresist composition and resist pattern-forming method

A photoresist composition comprising:

• a polymer component that includes a first structural unit represented by a formula (1) and a second structural unit represented by a formula (2), the first structural unit and the second structural unit being included in an identical polymer, or included in different polymers;
• an acid generator;
• and
• a compound represented by a formula (3),
• wherein R1 is a hydrogen atom, a fluorine atom, a hydroxyl group, or a monovalent organic group having 1 to 20 carbon atoms, R2 and R3 are each independently a hydrogen atom, a fluorine atom, a hydroxyl group, or a monovalent organic group having 1 to 20 carbon atoms, or taken together represent a cyclic structure having 3 to 10 carbon atoms together with a carbon atom bonded to R2 and R3, a is an integer from 1 to 6, provided that a plurality of R2 are either identical or different and a plurality of R3 are either identical or different when a is an integer equal to or larger than 2, R4 and R5 are each independently a hydrogen atom, a fluorine atom, a hydroxyl group, or a monovalent organic group having 1 to 20 carbon atoms, or taken together represent a cyclic structure having 3 to 10 carbon atoms together with a carbon atom bonded to R4 and R5, provided that some or all of hydrogen atoms of a cyclic structure represented by at least one of R4 and R5 are substituted with a substituent or unsubstituted, R6 is a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, R7 and R8 are each independently an alkyl group having 1 to 4 carbon atoms or an alicyclic group having 4 to 20 carbon atoms, or taken together represent a divalent alicyclic group together with a carbon atom bonded to R7 and R8, and R9 is an alkyl group having 1 to 4 carbon atoms or an alicyclic group having 4 to 20 carbon atoms, provided that some or all of hydrogen atoms of the alkyl group or the alicyclic group represented by R9 are substituted with a substituent or unsubstituted,
• R10-A−X+ (3)
• wherein R10 is a hydrogen atom or a monovalent organic group, A− is —N—SO2—Ra, —COO−, —O−, or —SO3−, provided that a fluorine atom is not bonded to a carbon atom bonded to A− when A− is —SO3− and bonded to a carbon atom, Ra is a linear or branched monovalent hydrocarbon group having 1 to 10 carbon atoms or a cyclic monovalent hydrocarbon group having 3 to 20 carbon atoms, provided that some or all of hydrogen atoms of the hydrocarbon group represented by Ra are substituted with a fluorine atom or unsubstituted, and X+ is an onium cation.