Positive resist composition and method of forming resist pattern

A positive resist composition comprising a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure,

• the base component (A) comprising a polymeric compound (A1) having an acid dissociable, dissolution inhibiting group in the structure thereof and comprising a structural unit (a0) represented by general formula (a0-1) shown below, and
• the acid-generator component (B) comprising an acid generator (B1) comprised of a compound represented by general formula (b1-1) shown below:
• wherein R represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms;
• R2 represents a divalent linking group;
• and R3 represents a cyclic group containing an —SO2— group within the ring skeleton thereof;
• and
• [Chemical Formula 2]
• R0—SO3−Z+ (b1-1)
• wherein R0 represents a hydrocarbon group of 1 to 12 carbon atoms which may have a substituent, with the provision that the carbon atom adjacent to the sulfur atom within the —SO3− group has no fluorine atom bonded thereto;
• and Z+ represents an organic cation.