Patent ID: 7989896

Claim:
A semiconductor device, comprising: a first N-type transistor formed on a semiconductor substrate, the first N-type transistor containing a first gate dielectric film and a first gate electrode; a first P-type transistor formed on the semiconductor substrate, the first P-type transistor containing a second gate dielectric film and a second gate electrode, the second gate dielectric film being made of the same material as the first gate dielectric film and having the same film thickness as the first gate dielectric film, the second gate electrode being made of the same material as the first gate electrode and having the same film thickness as the first gate electrode; a second N-type transistor formed on the semiconductor substrate, the second N-type transistor containing a third gate dielectric film and a third gate electrode, the third gate dielectric film consisting of a first insulator layer, a lanthanum oxide layer on the first insulator layer, and a first high dielectric constant insulator layer on the lanthanum oxide layer, the third gate electrode consisting of a first metal layer and a first semiconductor layer on the first metal layer, a threshold voltage of the second N-type transistor is lower than that of the first N-type transistor; and a second P-type transistor formed on the semiconductor substrate, the second P-type transistor containing a fourth gate dielectric film and a fourth gate electrode, the fourth gate dielectric film consisting of a second insulator layer, an aluminum oxide layer on the second insulator layer, and a second high dielectric constant insulator layer on the aluminum oxide layer, the fourth gate electrode consisting of a second metal layer and a second semiconductor layer on the second metal layer, the second high dielectric constant insulator layer being made of the same material as the first high dielectric constant insulator layer and having the same film thickness as the first high dielectric constant insulator layer, the second metal layer being made of the same material as the first metal layer and having the same film thickness as the first metal layer, the second semiconductor layer being made of the same material as the first semiconductor layer and having the same film thickness as the first semiconductor layer, a threshold voltage of the second P-type transistor is lower than that of the first P-type transistor.