Positive resist composition and method of forming resist pattern

A positive resist composition comprising a resin 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,

• said resin component (A) comprising a structural unit (a0) represented by general formula (a0) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of groups that exhibit aromaticity ,and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group and a structural unit (a3) represented by general formula (a3-1) shown below:
• wherein R represents a hydrogen atom, a lower alkyl group of 1 to 5 carbon atoms or a halogenated lower alkyl group of 1 to 5 carbon atoms;
• Q represents —NH—, —NR01—, —NH—R02—, —NR01—R02—,—O—, —O—R02—O—C(O)—, —NH—C(O)—NH— or —O—R02—NH—C(O)—NH—, wherein R01 represents a lower alkyl group of 1 to 5 carbon atoms, and R02 represents a linear alkylene group of 1 to 5 carbon atoms which may have a substituent;
• R6 represents a lower alkyl group of 1 to 5 carbon atoms or an alkoxy group of 1 to 5 carbon atoms;
• p represents an integer of 1 to 3;
• and q represents an integer of 0 to 2
• wherein R represents a hydrogen atom, a lower alkyl group of 1 to 5 carbon atoms or a halogenated lower alkyl group of 1 to 5 carbon atoms;
• and j is an integer of 1 to 3.