A CMOSFET in which a p-type gate electrode and an n-type gate electrode are formed on a silicon substrate. The p-type gate electrode includes, in order, a p-type polycrystalline silicon layer and a tungsten silicide layer. The n-type gate electrode includes, in order, an n-type polycrystaline silicon layer and a tungsten silicide layer. A carbon-containing polycrystalline silicon layer, which is an impurity thermal diffusion prevention layer to suppress the interdiffusion of impurities, is provided between the p-type polycrystalline silicon layer and the tungsten silicide layer.