Method for fabricating a transistor using a SOI wafer

1. A method comprising:

forming a first gate conductive layer pattern, a gate insulation layer pattern, and a silicon layer pattern over an SOI substrate comprising a substrate layer, a middle insulation layer formed over the substrate layer and a silicon layer formed over the middle insulation layer, wherein the silicon layer pattern is formed by etching the silicon layer;

forming device isolation insulation layers over and contacting the middle insulation layer;

forming a gate by forming a second gate conductive layer over the first gate conductive layer pattern and then etching the first gate conductive layer pattern and the second gate conductive layer to also form first gate conductive layer spacers on and contacting the gate insulating layer pattern and a sidewall of the device isolation insulation layers;

forming insulating layer spacers spaced apart from a respective first gate conductive layer spacer and on and contacting sidewalls of the gate;

forming a source and drain conductive layer adjacent to and contacting the first gate conductive layer spacers and the insulating layer spacers and over and contacting an exposed portion of the SOI substrate;

forming a salicide layer over each of the gate and the source and drain conductive layer.

2. The method of claim 1 , wherein forming the first gate conductive layer pattern, the gate insulation layer pattern and the silicon layer pattern comprises:

forming a gate insulation layer and a first gate conductive layer over the SOI substrate, wherein the gate insulation layer is formed over the silicon layer;

selectively etching the first gate conductive layer, the gate insulation layer, and the silicon layer to form the first gate conductive layer pattern, the gate insulation layer pattern, and the silicon layer pattern.

3. The method of claim 2 , wherein the exposed portion of the SOI substrate comprises the silicon layer pattern, which is exposed when forming the spacers.

4. The method of claim 1 , wherein forming the device isolation insulation layer comprises:

forming an insulation layer covering the first gate conductive layer pattern, the insulation layer having a thickness of 2000 to 5000 Å; and

performing chemical mechanical polishing on the insulation layer to expose the top surface of the first gate conductive layer pattern.

5. The method of claim 1 , wherein etching the first gate conductive layer pattern and the second gate conductive layer comprises forming a mask pattern over and contacting the second gate conductive layer and then etching the second gate conductive layer and the first gate conductive layer pattern.

6. The method of claim 5 , wherein forming the source and drain conductive layer comprises:

depositing a conductive layer covering the mask pattern;

performing chemical mechanical polishing on the conductive layer using the mask pattern as a polishing stop layer; and

etching the conductive layer to recess the source and drain conductive layer and to expose the top surface of the device isolation insulation layer and a top portion of the spacers.

7. The method of claim 6 , further comprising removing the mask pattern to expose the gate.

8. The method of claim 1 , wherein the gate insulation layer pattern comprises an etch stop layer for etching the gate.

9. The method of claim 1 , wherein the gate and the source and drain conductive layer each comprise a polysilicon layer.

10. The method of claim 1 , wherein the salicide layer comprises at least one of Ti-based salicide, Co-based salicide, Ta-based salicide, and Ni-based salicide.

11. A method comprising:

providing a SOI substrate comprising a substrate layer, an insulation layer formed over and contacting the substrate layer, and a silicon layer formed over and contacting the insulation layer;

forming a silicon layer pattern by etching the silicon layer, a first gate insulating layer pattern over and contacting the silicon layer pattern, a first gate conductive layer pattern over and contacting the first gate insulating layer pattern, and a second gate conductive layer pattern over and contacting the first gate conductive layer pattern, a device isolation insulation layer spaced apart from the first and second gate conductive layer patterns and over and contacting the insulation layer of the SOI substrate and a sidewall of the silicon layer pattern, and a first gate conductive layer pattern spacer over and contacting a sidewall of the device isolation insulation layer;

forming an insulating layer spacer over and contacting the uppermost surface of the first gate insulating layer pattern and a sidewall of the first and second gate conductive layer patterns;

forming a source and drain conductive layer between the device isolation insulation layer and the first and second gate conductive layer patterns and over and contacting the uppermost surface of the silicon layer pattern and a respective sidewall of the insulating layer spacer, the first gate insulating layer pattern and the first gate conductive layer pattern spacer.

12. The method of claim 11 , wherein the uppermost surface of the source and drain conductive layer and the insulating layer spacer are coplanar.

13. The method of claim 11 , wherein the uppermost surface of the source and drain conductive layer is formed spatially above the uppermost surface of the first gate insulating layer pattern.