Method for fabricating semiconductor devices

A method for fabricating a semiconductor device, the method including performing the following steps at least twice:

• depositing an insulator comprised of a single layer film of silicon oxide, silicon nitride, or silicon oxynitride or an insulator comprised of a laminated film of two or more films selected from the single layer films over a semiconductor substrate by a chemical vapor deposition method;
• and
• performing a plasma treatment to said insulator in an atmosphere containing oxygen atoms,
• wherein said plasma treatment is a treatment of the plasma mainly composed of ions containing oxygen atoms.

A method for fabricating a semiconductor device, the method comprising:

• (a) forming a laminated film by performing the following steps at least twice:
• depositing an insulator made of silicon oxide over a semiconductor substrate by a chemical vapor deposition method;
• and performing a plasma treatment to said deposited insulator in an atmosphere containing oxygen atoms;
• (b) patterning said laminated film so that a relatively thick insulator comprised of said laminated film can be left at least in a thick-film region over said semiconductor substrate;
• (c) forming a relatively thin insulator in a thin-film region over said semiconductor substrate;
• and
• (d) forming gate electrodes in said thick-film region and said thin-film region,
• wherein said plasma treatment is a treatment with plasma mainly comprised of ions containing oxygen atoms.