Method of stressing a semiconductor layer

1. A method of forming a stressed semiconductor layer, the method comprising:

forming, in a surface of a semiconductor structure having a semiconductor layer in contact with an insulator layer having a viscosity, at least two first trenches having a first depth in a first direction;

introducing, through said at least two first trenches, a stress in said semiconductor layer and temporarily decreasing, by annealing, the viscosity of said insulator layer; and

forming in said first direction first isolation trenches delimiting a first dimension of at least one transistor to be formed in said semiconductor structure by extending said at least two first trenches from a first depth to a second depth.

2. The method of claim 1 , wherein introducing the stress in said semiconductor layer comprises introducing a first material through said at least two first trenches and annealing the first material, and wherein extending said at least two first trenches from the first depth to a second depth comprises at least partially removing said first material.

3. The method of claim 2 , wherein introducing said first material comprises:

implanting atoms of said first material into a region of said semiconductor layer underlying each of said at least two first trenches; or

depositing said first material to at least partially fill each of said at least two first trenches, and wherein annealing the first material comprises heating said first material.

4. The method of claim 2 , wherein introducing said first material comprises implanting atoms of said first material into regions of said semiconductor layer, wherein said first depth of said at least two first trenches does not extend into said semiconductor layer.

5. The method of claim 4 , wherein said first material is germanium.

6. The method of claim 2 , wherein introducing said first material comprises depositing said first material to at least partially fill each of said at least two first trenches, and said first depth of said at least two first trenches extends through said semiconductor layer and at least partially into said insulator layer.

7. The method of claim 6 , wherein introducing said first material comprises depositing a metal to at least partially fill said at least two first trenches.

8. The method of claim 6 , wherein said first material has a first coefficient of thermal expansion and said semiconductor layer has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion.

9. The method of claim 6 , wherein said first material has a first coefficient of thermal expansion and the semiconductor layer has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion, the method further comprising, prior to temporarily decreasing the viscosity of said insulator layer:

forming, in said surface of said semiconductor structure, at least two second trenches in a second direction;

depositing a second material to at least partially fill each of said at least two second trenches, wherein said second material has a third coefficient of thermal expansion that is different from the first and second coefficients of thermal expansion; and

forming second isolation trenches in said second direction delimiting a second dimension of said at least one transistor by extending said at least two second trenches from a first depth to a second depth.

10. The method of claim 1 , further comprising forming at least two second isolation trenches in a second direction delimiting a second dimension of said at least one transistor.

11. The method of claim 10 , wherein forming said at least two second isolation trenches is performed after temporarily decreasing the viscosity of the insulator layer.

12. The method of claim 1 , wherein said annealing comprises annealing between 950° C. and 1150° C. for at least 20 minutes.

13. The method of claim 1 , wherein said semiconductor structure is an SOI (semiconductor on insulator) structure.

14. The method of claim 1 , wherein said semiconductor layer comprises a plurality of semiconductor fins.

15. A method comprising:

in a semiconductor structure that includes a semiconductor layer located on an insulator layer having a viscosity, forming a plurality of trenches having a first depth in a first direction;

introducing a material in the plurality of trenches;

stressing the semiconductor layer and temporarily decreasing the viscosity of the insulator layer by annealing the semiconductor structure; and

after annealing, forming first isolation trenches in the first direction for delimiting in a first dimension a transistor to be formed in the semiconductor structure by extending the two trenches from a first depth to a second depth, the second depth being deeper than the first depth.

16. The method of claim 15 , wherein introducing the material comprises depositing the material to at least partially fill the trenches.

17. The method of claim 15 , wherein the material has a first coefficient of thermal expansion and the semiconductor layer has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion.

18. The method of claim 15 , wherein the material is germanium.

19. The method of claim 15 , wherein the second depth extends into a semiconductor substrate of the structure that is located below the semiconductor layer and the insulator layer.

20. The method of claim 15 , wherein the first depth of the plurality of trenches does not extend into the semiconductor layer located on the insulator layer.

21. The method of claim 20 , wherein introducing the material comprises implanting atoms of the material into a region of the semiconductor layer that underlies the plurality of trenches.

22. The method of claim 15 , further comprising forming the transistor in the semiconductor structure.

23. A method comprising:

in a semiconductor structure that includes a semiconductor layer located on an insulator layer having a viscosity, forming a plurality of trenches having a first depth in a first direction;

introducing a material in the plurality of trenches;

stressing the semiconductor layer and temporarily decreasing the viscosity of the insulator layer by annealing the semiconductor structure;

after annealing the semiconductor structure, forming first isolation trenches in the first direction for delimiting in a first dimension a transistor to be formed in the semiconductor structure by extending the two trenches from a first depth to a second depth, the second depth being deeper than the first depth; and

forming the transistor in the semiconductor structure.

24. The method of claim 23 , wherein introducing the material comprises depositing the material to at least partially fill the trenches.

25. The method of claim 23 , wherein the material has a first coefficient of thermal expansion and the semiconductor layer has a second coefficient of thermal expansion that is different from the first coefficient of thermal expansion.

26. The method of claim 23 , wherein the material is germanium.