Positive resist composition and base material carrying layer of the positive resist composition

A base material comprising:

• an organic polymer layer as a first layer formed on a substrate;
• and
• a second resist layer formed on said organic polymer layer, said second resist layer being composed of a positive composition and having a thickness of from 50 to 200 nm, said positive composition comprising:
• (A) an alkali-soluble polysiloxane resin;
• (B) an acid generator composed of a compound which generates an acid upon irradiation of active light or radiant ray;
• and
• (C) a compound in which at least one hydrogen atom of the phenolic hydroxyl group or carboxyl group of the compound is substituted with an acid-decomposable group,
• wherein said Ingredient (A) is an alkali-soluble polysiloxane resin comprising (a1) a siloxane unit containing an alkali-soluble group, and (a2) a siloxane unit containing an alkali-insoluble group, said alkali-insoluble group having no acid-decomposable group.