A semiconductor device includes first and second MIS transistors and a dummy element. The first MIS transistor includes a first gate insulating film which includes a first high-k insulating film formed on a first active region and contains an adjusting metal. The second MIS transistor includes a second gate insulating film which includes a second high-k insulating film formed on a second active region and is free of the adjusting metal. The dummy element includes a dummy gate insulating film which includes a dummy high-k insulating film formed on a dummy active region and at least a portion of which is free of the adjusting metal. The first active region is formed in a second conductivity type first well region. The second active region is formed in a first conductivity type second well region. The dummy active region is formed in a second conductivity type third well region.