A method of manufacturing a semiconductor device include a step of forming an
insulating
layer, which is obtained by building up a first oxide film, a nitride film and
a second oxide film on a substrate in the order mentioned, and a Salicide step
of forming a Salicide-structure gate electrode on the insulating film. A silicidation
reaction between the substrate surface and an N+ diffusion region is prevented
in the Salicide step by causing the insulating layer to remain even in a region
on the substrate besides that immediately underlying the gate electrode.
