Rotational shear stress for charge carrier mobility modification

1. A method for forming a semiconductor structure comprising:

providing a semiconductor substrate having an active region mesa surrounded by an isolation trench;

forming a first isolation region having a first stress into the isolation trench;

forming a second isolation region having a second stress different than the first stress into the isolation trench, where the first isolation region and the second isolation region are sized and positioned to rotationally shear stress the active region mesa.

2. The method of claim 1 wherein only one of the first isolation region and the second isolation region contacts the active region mesa.

3. The method of claim 1 wherein both of the first isolation region and the second isolation region contact the active region mesa.

4. The method of claim 1 wherein the rotational shear stress is in a clockwise direction.

5. The method of claim 1 wherein the rotational shear stress is in a counter clockwise direction.

6. The method of claim 1 wherein when forming the first isolation region and the second isolation region:

the isolation trench is completely filled with a first isolation material;

a portion of the first isolation material is removed to form a void and the first isolation region; and

the second isolation region is formed into the void.

7. The method of claim 6 wherein the second isolation region is formed by:

filling the void with a silicon material; and

oxidizing the silicon material to form a silicon oxide material.

8. The method of claim 7 wherein the silicon material is selected from the group consisting of amorphous silicon materials and polysilicon materials.