Abstract: After forming a silicon nitride film 14 on a silicon oxide film 12 covering one main surface of a semiconductor substrate 10 by a CVD method, argon ions Ar+ are doped to a part (where oxidation speed should be reduced) of the silicon nitride film 14 by an ion doping process using a resist layer as a mask in a condition of acceleration voltage at 100 keV and a dose amount of 5×1015 inos/cm2. Thereafter, by performing a thermal oxidation process to the silicon nitride film 14, a thin silicon oxide film 18a is formed in a non-ion doped part and a thick silicon oxide film 18b is formed in an ion doped part. This method for forming silicon oxide films can be applied to a method for manufacturing capacitors of a MOS type IC, etc. Moreover, a silicon oxynitride film can be used instead of the silicon nitride film.

Abstract: After forming a silicon nitride film 14 on a silicon oxide film 12 covering one main surface of a semiconductor substrate 10 by a CVD method, argon ions Ar+ are doped to a part (where oxidation speed should be reduced) of the silicon nitride film 14 by an ion doping process using a resist layer as a mask in a condition of acceleration voltage at 100 keV and a dose amount of 5×1015 inos/cm2. Thereafter, by performing a thermal oxidation process to the silicon nitride film 14, a thin silicon oxide film 18a is formed in a non-ion doped part and a thick silicon oxide film 18b is formed in an ion doped part. This method for forming silicon oxide films can be applied to a method for manufacturing capacitors of a MOS type IC, etc. Moreover, a silicon oxynitride film can be used instead of the silicon nitride film.