Positive photosensitive composition

A positive photosensitive composition, comprising:

• (a) a compound having a group represented by the following general formula (Ia) which decomposes by the action of an acid to enhance its solubility in an alkaline developing solution;
• and
• (b) a compound which generates an acid upon irradiation with actinic rays or radiation:
• wherein R1a and R2a may be the same or different and each represent a hydrogen atom or C1-4 alkyl group;
• Wa represents a single bond or divalent organic group;
• and R3a represents a group which decomposes by the action of an acid and is selected from the group consisting of —COOA0, —O—A0 and —O—C(═O)—O—A0, wherein A0 represents —C(R01)(R02)(R03), —Si(R01)(R02)(R03) or —C(R04)(R05)—O—R06, where R01, R02, R03, R04 and R05 may be the same or different and each represents a hydrogen atom, an alkyl group, a cycloalkyl group, an alkenyl group or an aryl group, R06 represents an alkyl group or an aryl group, two of R01 to R03 may be connected to each other to form a ring or two of R04 to R06 may be connected to each other to form a ring, with the proviso that at least two of R01 to R03 are groups other than a hydrogen atom.