A gate insulation film is formed on a semiconductor substrate, gate electrodes
are formed on the gate insulation film, and source/drain diffusion layers are formed.
A silicon nitride films is formed on a side wall of the gate electrodes, a silicon
oxide film is formed on the overall surface, and the silicon oxide film is etched
back to have the same height as that of the gate electrodes so that the surface
is flattened, and then the surface of the gate electrodes are etched by a predetermined
thickness to form a first stepped portion from the silicon oxide film, the first
stepped portion is filled up by a tungsten film, the surface of the tungsten film
is etched by a predetermined thickness so that a second stepped portion is formed,
and then the second stepped portion is filled by a silicon nitride films.