There is provided a semiconductor device having a metal silicide layer which can suppress the malfunction and the increase in power consumption of the device. The semiconductor device has a semiconductor substrate containing silicon and having a main surface, first and second impurity diffusion layers formed in the main surface of the semiconductor substrate, a metal silicide formed over the second impurity diffusion layer, and a silicon nitride film and a first interlayer insulation film sequentially stacked over the metal silicide. In the semiconductor device, a contact hole penetrating through the silicon nitride film and the first interlayer insulation film, and reaching the surface of the metal silicide is formed. The thickness of a portion of the metal silicide situated immediately under the contact hole is smaller than the thickness of a portion of the metal silicide situated around the contact hole.