Poly resistor and poly eFuse design for replacement gate technology

1. A method comprising:

forming an isolation region on a substrate, wherein the isolation region extends a depth into the substrate from a substrate surface;

forming a recess in the isolation region, wherein the recess is defined by a concave surface of the isolation region;

forming a first gate structure over the substrate surface and a second gate structure over the concave surface of the isolation region, wherein forming the first gate structure comprises forming a first gate stack over the substrate surface and a second gate stack over the concave surface of the isolation region, wherein a topmost layer of the first and second gate stacks is a hard mask layer;

removing the hard mask layer from the second gate stack; and

forming a first doped region and a second doped region in the substrate, wherein the first gate stack interposes the first doped region and the second doped region.

2. The method of claim 1 wherein the forming the first doped region and the second doped region in the substrate includes doping the second gate stack.

3. The method of claim 1 wherein the forming the first doped region and the second doped region in the substrate includes:

forming a recess in the substrate, wherein the recess is defined by a recessed surface of the substrate; and

performing an implantation process to form the first doped region and the second doped region in the substrate along the recessed surface.

4. The method of claim 1 further including:

forming a protection layer over the second gate stack; and

thereafter, forming a silicide feature in the first doped region and the second doped region.

5. The method of claim 4 further including removing the hard mask layer from the first gate stack after forming the silicide feature in the first doped region and the second doped region.

6. The method of claim 4 wherein the forming the protection layer over the second gate stack includes forming a resist protect oxide (RPO) layer over the second gate stack.

7. The method of claim 1 wherein the forming the first gate structure over the substrate surface and the second gate structure over the concave surface of the isolation region includes:

forming a metal gate transistor over the substrate surface; and

forming a resistive structure over the concave surface of the isolation region.

8. The method of claim 1 wherein the forming the recess in the isolation region, the recess being defined by the concave surface of the isolation region, includes etching the isolation region until a distance (d) between the substrate surface and a bottommost portion of the concave surface is about 10% of the depth (T) of the isolation region to about 70% of the depth (T) of the isolation region (0.10T <d <0.70T).

9. A method comprising:

forming an isolation region on a substrate having a substrate surface, wherein the isolation region has an isolation region surface that is in a plane lower than the substrate surface;

thereafter, forming a first gate structure over the substrate surface and a second gate structure over the isolation region surface, wherein the first gate structure and the second gate structure include a hard mask layer;

thereafter, removing the hard mask layer from the second gate structure;

thereafter, forming a source region and a drain region in the substrate, wherein the first gate structure interposes the source region and the drain region;

thereafter, forming a protection layer over the second gate structure;

thereafter, forming a silicide feature on the source region and the drain region;

thereafter, removing the hard mask layer from the first gate structure.

10. The method of claim 9 wherein the forming the isolation region on the substrate having the substrate surface, wherein the isolation region has the isolation region surface that is in a plane lower than the substrate surface, includes etching the isolation region to form a recess in the isolation region, wherein the recess is defined by a concave surface.

11. The method of claim 9 wherein:

the forming the first gate structure includes forming a first gate stack having a first gate stack that includes a gate dielectric layer disposed over the substrate, a gate electrode layer disposed over the gate dielectric layer, and the hard mask layer disposed over the gate electrode layer; and

the forming the second gate structure includes forming a second gate stack having a second gate stack that includes the gate dielectric layer disposed over the substrate, the gate electrode layer disposed over the gate dielectric layer, and the hard mask layer disposed over the gate electrode layer.

12. The method of claim 11 :

wherein the gate electrode layer includes a polysilicon layer; and

the forming the source region and the drain region in the substrate includes simultaneously doping the polysilicon layer of the second gate stack.

13. The method of claim 12 further including, after removing the hard mask layer from the first gate structure, replacing the polysilicon layer of the first gate stack with a metal layer.

14. The method of claim 11 further including, after removing the hard mask layer from the first gate structure, replacing a polysilicon gate electrode of the first gate structure with a metal gate electrode.

15. The method of claim 11 wherein the forming the source region and the drain region in the substrate, wherein the first gate structure interposes the source region and the drain region, includes:

forming a recess in the substrate, wherein the recess is defined by a recessed surface of the substrate that is in a plane lower than the substrate surface; and

performing an implantation process to form the source region and the drain region in the substrate along the recessed surface.

16. A method comprising:

providing a semiconductor substrate;

forming a shallow trench isolation in the semiconductor substrate;

etching the shallow trench isolation such that the shallow trench isolation has a concave surface that is in a plane lower than a surface of the semiconductor substrate;

forming a resistive structure over the concave surface of the shallow trench isolation; and

performing a salicidation process, wherein the resistive structure is protected during the salicidation process.

17. The method of claim 16 further including simultaneously a gate structure over the surface of the semiconductor substrate while forming the resistive structure.

18. The method of claim 17 wherein the performing the salicidation process, wherein the resistive structure is protected during the salicidation process, includes:

forming a silicide feature in a source region and a drain region, the source region and the drain region being interposed by the gate structure; and

forming a resist protection oxide layer over the resistive structure before forming the silicide feature.