Method of fabricating nonvolatile semiconductor memory devices with uniform sidewall gate length

A fabricating method of a nonvolatile semiconductor memory device, comprising:

• a first dielectric film formed on a main surface of a semiconductor substrate;
• a first gate electrode composed of a first conductive film formed on said first dielectric film;
• a cap dielectric film formed on said first gate electrode;
• a second dielectric film formed on a sidewall of said first gate electrode and said main surface;
• a second gate electrode composed of a second conductive film formed on said second dielectric film;
• and
• doped regions to be source and drain formed in said semiconductor substrate below said first gate electrode and said second gate electrode,
• said fabricating method comprising the steps of:
• (a) forming said first dielectric film on said main surface and then forming said first conductive film on said first dielectric film;
• (b) forming said cap dielectric film on said first conductive film;
• (c) planarizing a surface of said cap dielectric film by a CMP method;
• (d) forming said first gate electrode by patterning said cap dielectric film and said first conductive film;
• (e) forming said second dielectric film on the sidewall of said first gate electrode and said main surface and forming said second conductive film on said second dielectric film;
• and
• (f) etching back said second conductive film to form said second gate electrode.