Semiconductor device and manufacturing method thereof

1. A semiconductor device, comprising:

an active region formed on a semiconductor substrate;

an element isolation region formed on the semiconductor substrate so as to surround the active region; and

a gate electrode formed on the active region, wherein

a first element isolation region that causes tensile stress so as to improve carrier mobility in the active region is provided in the element isolation region,

the first element isolation region is formed in a trench arranged in the semiconductor substrate and has a first insulating film that causes the tensile stress and a void which is located so that the entire of the void is surrounded by the first insulating film,

the active region is an N-type MISFET (Metal Insulator Semiconductor Field Effect Transistor) region,

the first element isolation region is provided in a portion of the element isolation region which is adjacent to the active region in a gate length direction,

a second element isolation region is provided in a portion of the element isolation region which is adjacent to the active region in a gate width direction, and

the second element isolation region has a second insulating film formed in a trench arranged in the semiconductor substrate but has no void.

2. The semiconductor device according to claim 1 , further comprising another active region as a P-type MISFET region that is formed on the semiconductor substrate so as to be located next to the active region in the gate length direction and to be surrounded by the element isolation region, wherein the another active region has a gate length direction of <100> orientation.

3. The semiconductor device according to claim 1 , further comprising another active region as a P-type MISFET region that is formed on the semiconductor substrate so as to be located next to the active region in the gate width direction and to be surrounded by the element isolation region, wherein the another active region has a gate length direction of <100> orientation.

4. The semiconductor device according to claim 1 , wherein the first insulating film is formed from a silicon oxide film.

5. The semiconductor device according to claim 1 , wherein the first and second insulating films are formed from a silicon oxide film.

6. The semiconductor device according to claim 1 , wherein a width of the trench of the first element isolation region is narrower than a width of the trench of the second element isolation region.

7. The semiconductor device according to claim 1 , wherein a sidewall taper angle of the trench of the first element isolation region is smaller than a sidewall taper angle of the trench of the second element isolation region.

8. The semiconductor device according to claim 7 , wherein a width of an upper part of the trench of the first element isolation region is the same as a width of an upper part of the trench of the second element isolation region.

9. A semiconductor device, comprising:

an active region formed on a semiconductor substrate;

an element isolation region formed on the semiconductor substrate so as to surround the active region; and

a gate electrode formed on the active region,

wherein a first element isolation region that causes tensile stress so as to improve carrier mobility in the active region is provided in the element isolation region,

the first element isolation region is formed in a trench arranged in the semiconductor substrate and has a first insulating film that causes the tensile stress and a void which is located so that the entire of the void is surrounded by the first insulating film,

the active region is a P-type MISFET region, and the first element isolation region is provided in a portion of the element isolation region which is adjacent to the active region in a gate width direction,

a second element isolation region is provided in a portion of the element isolation region which is adjacent to the active region in a gate length direction, and

the second element isolation region has a second insulating film formed in a trench arranged in the semiconductor substrate but has no void.

10. The semiconductor device according to claim 9 , further comprising another active region as an N-type MISFET region that is formed on the semiconductor substrate so as to be located next to the active region in the gate length direction and to be surrounded by the element isolation region, wherein the another active region has a gate length direction of <110> orientation.

11. The semiconductor device according to claim 10 , wherein a portion of the element isolation region which is located between the active region and the another active region is divided by a substrate region that extends in the gate width direction, and the first element isolation region is provided also in one of the divided portions which is located adjacent to the another active region.

12. The semiconductor device according to claim 9 , further comprising another active region as an N-type MISFET region that is formed on the semiconductor substrate so as to be located next to the active region in the gate width direction and to be surrounded by the element isolation region, wherein the another active region has a gate length direction of <110> orientation.

13. The semiconductor device according to claim 12 , wherein the first element isolation region is provided also in a portion of the element isolation region which is adjacent to the another active region in the gate length direction.

14. The semiconductor device according to claim 9 , wherein the first and second insulating films are formed from a silicon oxide film.

15. The semiconductor device according to claim 9 , wherein a width of the trench of the first element isolation region is narrower than the width of the trench of the second element isolation region.