| 摘要 |
A positive resist composition and method for forming a resist pattern are provided which enable a resist pattern with excellent shape to be obtained. The resist composition includes a resin component (A) which exhibits increased alkali solubility under action of acid, an acid-generator component (B) which generates acid upon irradiation and an organic solvent (S) in which the components (A) and (B) are dissolved, the resin component (A) including a copolymer (A1) containing: a structural unit (a1) having an acetal-type protected group, a structural unit (a2) derived from an acrylate ester having a lactone-containing polycyclic group, which is represented by general formula (a2-1) shown below; and a structural unit (a3) derived from an acrylate ester having a polar group-containing aliphatic hydrocarbon group: wherein R represents a hydrogen atom, a fluorine atom, a lower alkyl group or a fluorinated lower alkyl group; R' represents a hydrogen atom, a lower alkyl group or an alkoxy group of 1 to 5 carbon atoms; and m represents 0 or 1.
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