A semiconductor device includes: an n-channel MIS transistor and a p-channel MIS transistor. An n-channel MIS transistor includes: a first gate insulating film having an amorphous layer or an epitaxial layer formed on a p-type semiconductor region between a first source/drain regions; and a first gate electrode having a stack structure formed with a first metal layer and a first compound layer. The first metal layer is formed on the first gate insulating film and made of a first metal having a work function of 4.3 eV or smaller, and the first compound layer is formed on the first metal layer and contains a compound of a second metal and a IV-group semiconductor. The second metal is different from the first metal. A p-channel MIS transistor includes a second gate electrode having a second compound layer containing a compound of the same composition as the first compound layer.