Semiconductor device and fabrication method for the same

1. A semiconductor device comprising a first transistor and a second transistor formed in a semiconductor substrate, the first transistor comprising:

a first gate insulating film formed on the semiconductor substrate; and

a first gate electrode formed on the first gate insulating film,

the second transistor comprising:

a second gate insulating film formed on the semiconductor substrate;

a cap film formed on the second gate insulating film; and

the first gate electrode formed on the cap film,

wherein the first gate insulating film includes a first insulating material with a first metal element diffused therein,

the cap film includes a second metal element which is different from the first metal element,

the second gate insulating film includes a second insulating material,

both of the first and second insulating materials include silicon and a third metal element, and the third metal element is different from the first and second metal elements, and

the first and second metal elements are not silicon.

2. The semiconductor device of claim 1 , wherein the first metal element is lanthanum.

3. The semiconductor device of claim 1 , wherein the second metal element is aluminum or tantalum.

4. The semiconductor device of claim 1 , wherein the first gate electrode includes titanium nitride.

5. The semiconductor device of claim 1 , further comprising a second gate electrode formed on and in contact with the first gate electrode.

6. The semiconductor device of claim 5 , wherein the second gate electrode is made of polysilicon.

7. The semiconductor device of claim 1 , wherein the third metal element is hafnium.