A semiconductor device includes a semiconductor substrate, a p-channel MIS transistor formed on the substrate, the p-channel transistor having a first gate dielectric formed on the substrate and a first gate electrode layer formed on the first dielectric, and an n-channel MIS transistor formed on the substrate, the n-channel transistor having a second gate dielectric formed on the substrate and a second gate electrode layer formed on the second dielectric. A bottom layer of the first gate electrode layer in contact with the first gate dielectric and a bottom layer of the second gate electrode layer in contact with the second gate dielectric have the same orientation and the same composition including Ta and C, and a mole ratio of Ta to a total of C and Ta, (Ta/(Ta+C)), is larger than 0.5.