It is made possible to control the effective work function of the gate electrode so that the transistor can have an optimum operating threshold voltage. A semiconductor device includes: a semiconductor substrate; a gate insulating film provided on the semiconductor substrate; a gate electrode provided on the gate insulating film; source/drain regions provided in the semiconductor substrate on both sides of the gate electrode; and a layer which is provided at an interface between the gate electrode and the gate insulating film, and contains an element having an electronegativity different from those of elements constituting the gate electrode and the gate insulating film. |