Semiconductor device and method of manufacturing semiconductor device

1. A semiconductor device comprising:

a first transistor including:

a first impurity layer of a first conduction type formed in a first region of a semiconductor substrate;

a first epitaxial semiconductor layer formed above the first impurity layer;

a first gate insulating film formed above the first epitaxial semiconductor layer;

a first gate electrode formed above the first gate insulating film; and

first source/drain regions of a second conduction type formed in the first epitaxial semiconductor layer and in the semiconductor substrate in the first region; and

a second transistor including:

a second impurity layer of the first conduction type formed in a second region of the semiconductor substrate;

a second epitaxial semiconductor layer formed above the second impurity layer and being thinner than the first epitaxial semiconductor layer;

a second gate insulating film formed above the second epitaxial semiconductor layer;

a second gate electrode formed above the second gate insulating film; and

second source/drain regions of the second conduction type formed in the second epitaxial semiconductor layer and in the semiconductor substrate in the second region.

2. The semiconductor device according to claim 1 , wherein

the first impurity layer and the second impurity layer have the same impurity concentration distribution.

3. The semiconductor device according to claim 1 , wherein

the first gate insulating film and the second gate insulating film have the same film thickness.

4. The semiconductor device according to claim 1 , further comprising:

a third transistor including:

a third impurity layer of the second conduction type formed in a third region of the semiconductor substrate;

a third epitaxial semiconductor layer formed above the third impurity layer;

a third gate insulating film formed above the third epitaxial semiconductor layer;

a third gate electrode formed above the third gate insulating film; and

third source/drain regions of the first conduction type formed in the third epitaxial semiconductor layer and the semiconductor substrate in the third region; and

a fourth transistor including:

a fourth impurity layer of the second conduction type formed in a fourth region of the semiconductor substrate;

a fourth epitaxial semiconductor layer formed above the fourth impurity layer and being thinner than the third epitaxial semiconductor layer;

a fourth gate insulating film formed above the fourth epitaxial semiconductor layer;

a fourth gate electrode formed above the fourth gate insulating film; and

fourth source/drain regions of the first conduction type formed in the fourth epitaxial semiconductor layer and the semiconductor substrate in the fourth region.

5. The semiconductor device according to claim 4 , wherein

the third impurity layer and the fourth impurity layer have the same impurity concentration distribution.

6. The semiconductor device according to claim 4 , wherein

the third gate insulating film and the fourth gate insulating film have the same film thickness.

7. The semiconductor device according to claim 4 , wherein

the first epitaxial semiconductor layer and the third epitaxial semiconductor layer have the same film thickness, and

the second epitaxial semiconductor layer and the fourth epitaxial semiconductor layer have the same film thickness.

8. The semiconductor device according to claim 1 , further comprising:

a fifth transistor including:

a fifth impurity layer of the first conduction type formed in a fifth region of the semiconductor substrate;

a fifth epitaxial semiconductor layer formed above the fifth impurity layer and having the same film thickness as the second epitaxial semiconductor layer;

a fifth gate insulating film formed above the fifth epitaxial semiconductor layer and being thicker than the first gate insulating film;

a fifth gate electrode formed above the fifth gate insulating film; and

fifth source/drain regions of the second conduction type formed in the fifth epitaxial semiconductor layer and the semiconductor substrate in the fifth region.

9. The semiconductor device according to claim 4 , further comprising:

a fifth transistor including:

a fifth impurity layer of the first conduction type formed in a fifth region of the semiconductor substrate;

a fifth epitaxial semiconductor layer formed above the fifth impurity layer and having the same film thickness as the second epitaxial semiconductor layer;

a fifth gate insulating film formed above the fifth epitaxial semiconductor layer and being thicker than the first gate insulating film;

a fifth gate electrode formed above the fifth gate insulating film; and

fifth source/drain regions of the second conduction type formed in the fifth epitaxial semiconductor layer and the semiconductor substrate in the fifth region.

10. The semiconductor device according to claim 9 , further comprising:

a sixth transistor including:

a sixth impurity layer of the second conduction type formed in a sixth region of the semiconductor substrate;

a sixth epitaxial semiconductor layer formed above the sixth impurity layer and having the same film thickness as the second epitaxial semiconductor layer;

a sixth gate insulating film formed above the sixth epitaxial semiconductor layer and being thicker than the first gate insulating film;

a sixth gate electrode formed above the sixth gate insulating film; and

sixth source/drain regions of the first conduction type formed in the sixth epitaxial semiconductor layer and the semiconductor substrate in the sixth region.