Positive-working photoresist composition for thick film formation

A chemical-amplification positive-working photoresist composition for the formation of a photoresist layer on a substrate surface which comprises:

• (A) a photoacid generating agent;
• (B) an alkali-insoluble resin capable of being imparted with an increased alkali solubility by interacting with an acid;
• (C) an alkali-soluble resin;
• and (D) an organic solvent,
• wherein the component (B) is a resin containing the monomeric units represented by the following formula:
• wherein R1 is a hydrogen atom or a methyl group, R2 is an alkyl group having 1 to 5 carbon atoms and X is a divalent hydrocarbon group to form a cyclic structure of 5 to 20 carbon atom members including the carbon atom to which the group denoted by X is bonded, and
• wherein the component (C) includes (C1) a copolymer of hydroxystyrene and styrene, and contains at least 80% by mass of hydroxystyrene units,
• with the proviso that the content of the component (C1) relative to 100 parts by mass of the total amount of the components (B) and (C) does not exceed 15 parts by mass.