Method for manufacturing a photoresist pattern defining a small opening and method for manufacturing semiconductor device using the same

A method for manufacturing a semiconductor device, comprising:

• providing a semiconductor substrate;
• forming a material film to be patterned on the semiconductor substrate;
• forming a photoresist film on the material film by coating thereon a photoresist composition comprising:
• (i) either a polymer mixture I containing a polymer A in which an acid-labile di-alkyl malonate group is pendant to the polymer backbone and a polymer B in which a group that thermally decomposes at a temperature lower than the glass transition temperature of the polymer B itself is pendant to the polymer backbone, or a polymer mixture II containing the polymer B and a polymer C including (meth)acrylate as a monomer;
• and (ii) a photosensitive acid generator;
• forming a photoresist pattern defining an opening by patterning the photoresist film;
• reducing the size of the opening by performing a first thermal flow process on the photoresist pattern;
• and
• etching the material film using the photoresist pattern as a mask to form either a contact hole or a damascene area in the material film, whereby the contact hole or the damascene area have the reduced size of the opening in the photoresist film.