Semiconductor device and method for manufacturing semiconductor device

1. A semiconductor device comprising:

a semiconductor substrate;

a gate dielectrics formed on the semiconductor substrate and including a silicon oxide film containing a metallic element, the silicon oxide film containing the metallic element including a first region near a lower surface thereof, a second region near an upper surface thereof, and a third region between the first and second regions, the metallic element contained in the silicon oxide film having a density distribution in a thickness direction of the silicon oxide film, a peak of the density distribution existing in the third region; and

an electrode formed on the gate dielectrics.

2. The semiconductor device according to claim 1 , wherein the silicon oxide film further contains nitrogen, the nitrogen contained in the silicon oxide film having a density distribution in the thickness direction of the silicon oxide film, a peak of the nitrogen density distribution existing in the second region.

3. The semiconductor device according to claim 1 , wherein the metallic element contained in the silicon oxide film is selected from a group consisting of Zr, Hf, Al and La.

4. The semiconductor device according to claim 1 , wherein the silicon oxide film further contains another metallic element selected from a group consisting of Zr, Hf, Al and La.