Mechanism for forming semiconductor device with gate

1. A semiconductor device, comprising:

a semiconductor substrate;

an isolation structure in the semiconductor substrate and surrounding an active region of the semiconductor substrate;

a gate extending along a lengthwise direction thereof and over the semiconductor substrate, wherein the gate has an intermediate portion over the active region and two end portions connected to the intermediate portion, the end portions are over the isolation structure, the gate has an upper surface and a lower surface opposite to the upper surface, and the lower surface is between the upper surface and the semiconductor substrate; and

a support film over the isolation structure and covering the isolation structure, at least one of the end portions of the gate and a sidewall of the at least one of the two end portions of the gate, wherein the sidewall extends along a widthwise direction of the gate perpendicular to the lengthwise direction of the gate, wherein the support film exposes the active region and the intermediate portion of the gate, the support film covers a portion of the upper surface, the support film and the active region surrounded by the isolation structure do not overlap with each other, and the support film is a continuous film which continuously covers the isolation structure and both the end portions of the gate.

2. The semiconductor device as claimed in claim 1 , wherein the semiconductor substrate has lightly doped regions at two opposite sides of the gate.

3. The semiconductor device as claimed in claim 1 , wherein the support film comprises an insulating material.

4. The semiconductor device as claimed in claim 3 , wherein the support film comprises silicon oxides, silicon oxynitrides, silicon nitrides or silicon carbonitrides.

5. The semiconductor device as claimed in claim 1 , wherein a the thickness of the support film ranges from 5 Å to 5000 Å.

6. The semiconductor device as claimed in claim 1 , wherein a the thickness of the support film ranges from 5 Å to 1000 Å.

7. The semiconductor device as claimed in claim 1 , wherein a thickness of the support film is substantially the same as a gate length of the gate.

8. The semiconductor device as claimed in claim 1 , wherein the support film continuously surrounds the active region.

9. The semiconductor device as claimed in claim 1 , wherein the gate has a gate length shorter than or equal to 100 nm.

10. The semiconductor device as claimed in claim 1 , wherein the support film has an opening exposing the intermediate portion of the gate and the active region.

11. The semiconductor device as claimed in claim 10 , wherein a gate length of the gate is less than a width of the opening.

12. The semiconductor device as claimed in claim 10 , wherein the opening further exposes a portion of the isolation structure.

13. The semiconductor device as claimed in claim 12 , wherein the portion of the isolation structure exposed by the opening surrounds the active region.

14. A semiconductor device, comprising:

a semiconductor substrate;

an isolation structure in the semiconductor substrate and surrounding an active region of the semiconductor substrate;

a gate extending along a lengthwise direction thereof and over the semiconductor substrate, wherein the gate has an intermediate portion over the active region and two end portions connected to the intermediate portion, the end portions are over the isolation structure; and

a support film over the isolation structure and covering the isolation structure, at least one of the end portions of the gate and a sidewall of the at least one of the two end portions of the gate, wherein the sidewall extends along a widthwise direction of the gate perpendicular to the lengthwise direction of the gate, wherein the support film exposes the active region and the intermediate portion of the gate, the support film and the active region surrounded by the isolation structure do not overlap with each other, and the support film is a continuous film which continuously covers the isolation structure and both the end portions of the gate.

15. The semiconductor device as claimed in claim 14 , wherein a thickness of the support film is substantially the same as a gate length of the gate.

16. The semiconductor device as claimed in claim 14 , wherein the support film has an opening exposing the intermediate portion of the gate and the active region.

17. The semiconductor device as claimed in claim 14 , wherein the support film comprises an insulating material.

18. A semiconductor device, comprising:

a semiconductor substrate;

an isolation structure in the semiconductor substrate and surrounding an active region of the semiconductor substrate;

a gate extending along a lengthwise direction thereof and over the semiconductor substrate, wherein the gate has an intermediate portion over the active region and two end portions connected to the intermediate portion, the end portions are over the isolation structure, the gate has an upper surface and a lower surface opposite to the upper surface, and the lower surface is between the upper surface and the semiconductor substrate; and

a support film over the isolation structure and covering the isolation structure, a sidewall of the at least one of the two end portions of the gate, wherein the sidewall extends along a widthwise direction of the gate perpendicular to the lengthwise direction of the gate, wherein the support film exposes the active region and the intermediate portion of the gate, the support film and the active region surrounded by the isolation structure do not overlap with each other, and the support film is a continuous film which continuously covers the isolation structure and both the end portions of the gate.

19. The semiconductor device as claimed in claim 18 , wherein the support film covers a portion of the upper surface.

20. The semiconductor device as claimed in claim 18 , wherein the support film has an opening exposing the intermediate portion of the gate and the active region.