Method for manufacturing semiconductor device

A method of manufacturing a semiconductor device comprising:

• applying an insulating film composition containing an insulating film precursor and a pore-generating material onto a semiconductor substrate;
• first heat treating said insulating film composition at a first temperature, not exceeding 350° C., in an inert-gas ambient to polymerize said insulating film precursor and form a non-porous film;
• forming a chemical mechanical polishing (CMP) stopper film on said non-porous insulating film;
• forming a resist pattern on said CMP stopper film;
• dry etching said CMP stopper film and said non-porous insulating film using said resist pattern as a mask to form a trench in said non-porous insulating film;
• removing said resist pattern by ashing;
• cleaning said semiconductor substrate after the ashing;
• after the cleaning, second heat treating said non-porous insulating film at a second temperature that is no higher than the first temperature in an oxidizing-gas ambient, removing said pore-generating material from said non-porous insulating film, thereby forming a porous insulating film;
• forming a barrier metal film on said CMP stopper film and on inner surfaces of said trench;
• forming a copper layer on said barrier metal film, filling said trench;
• and
• polishing said copper layer and said barrier metal film by CMP, thereby forming a copper wiring.