A semiconductor device having a silicide film above source-drain regions comprises an element isolation insulating film which is provided so as to enclose an element forming region of a semiconductor substrate whose main component is silicon and contains silicon oxide as a main component, a gate electrode which is formed above the element forming region via a gate insulating film, diffused layers which are formed in the semiconductor substrate so as to sandwich a channel region below the gate electrode, semiconductor regions which are formed so as to sandwich the channel region and diffused regions and are composed of semiconductor material whose lattice constant differs from that of silicon, a silicon nitride film which is formed between the semiconductor regions and the element isolation insulating film and above the lowest part of the semiconductor regions, and a conducting film which is formed at the surface of the semiconductor regions.