A semiconductor device includes n- and p-type semiconductor regions separately formed on a substrate, an interlayer insulator formed on the substrate and having first and second trenches formed to reach the n- and p-type regions. There are further included first and second gate insulators formed inside of the first and second trenches, a first metal layer formed inside of the first trench via the first gate insulator, a second metal layer formed in a thickness of 1 monolayer or more and 1.5 nm or less inside of the second trench via the second gate insulator, a third metal layer formed on the second metal layer and containing at least one of a simple substance, a nitride, a carbide and an oxide of at least one metal element of alkaline earth metal elements and group III elements, first and second source/drain regions formed on the n- and p-type regions.