A positive photosensitive composition includes (A) a resin having a
repeating unit with a lactone structure of 5.0 or below an Onishi
parameter and having any of repeating units of Formula (I) that when
acted on by an acid, generates a carboxylic acid, and (B) a compound that
when exposed to actinic rays or radiation, generates an acid,
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wherein each of R.sub.1, R.sub.2 and R.sub.3 independently represents a
substituted or unsubstituted alkyl group or a substituted or
unsubstituted cycloalkyl group, provided that R.sub.2 and R.sub.3 may be
bonded with each other to thereby form a ring structure, and Ra
represents a hydrogen atom, an alkyl group or a group of the formula
--CH.sub.2--O--Ra.sub.2 in which Ra.sub.2 represents a hydrogen atom, an
alkyl group or an acyl group, the structure of Formula (I) having a van
der Waals volume of 306.times.10.sup.-30 m.sup.3 or less.