CMP fabrication solution for split gate memory embedded in HK-MG process

1. A semiconductor device, comprising:

a substrate;

at least one logic device on the substrate, wherein the at least one logic device has a high-k metal gate structure;

a split gate memory device on the substrate, the split gate memory device comprising a memory gate and a select gate adjacent to and electrically isolated with each other, wherein the select gate has a flat top surface, and the memory gate has an inclined top surface; and

a dielectric layer on the substrate and between the at least one logic device and the split gate memory device, wherein a top surface of the dielectric layer and the flat top surface of the select gate are coplanar, and the elevation of the select gate is higher than the elevation of the memory gate.

2. The semiconductor device of claim 1 , wherein a top of the select gate and a top of the at least one logic device are substantially at the same elevation.

3. The semiconductor device of claim 1 , wherein an elevation difference between a top of the select gate and a top of the memory gate is greater than ten percent of a height of the select gate.

4. The semiconductor device of claim 1 , wherein the select gate is formed from polysilicon.

5. The semiconductor device of claim 1 , wherein the split gate memory device further comprises an intermediate structure between the memory gate and the select gate.

6. The semiconductor device of claim 5 , wherein the intermediate structure comprises a bottom layer, a trap layer and a top layer stacked in sequence.

7. The semiconductor device of claim 5 , wherein the intermediate structure comprises an oxide/nitride/oxide stacked structure.

8. A method for manufacturing a semiconductor device, comprising:

providing a substrate;

forming at least one logic device on the substrate, wherein the at least one logic device comprises a dummy gate;

forming a split gate memory device on the substrate, wherein the split gate memory device comprises a memory gate and a select gate adjacent to and electrically isolated with each other, the select gate has a flat top surface, and the memory gate has an inclined top surface, and a top of the select gate and a top of the dummy gate are substantially at the same elevation;

forming a dielectric layer to cover the at least one logic device and the split gate memory device;

polishing the dielectric layer to expose the top of the select gate and the top of the dummy gate, wherein after the operation of polishing the dielectric layer is completed, a top surface of the dielectric layer and the flat top surface of the select gate are coplanar, and the elevation of the select gate is higher than the elevation of the memory gate; and

replacing the dummy gate with a metal gate.

9. The method of claim 8 , wherein the operation of forming the split gate memory device comprises forming an elevation difference between the top of the select gate and a top of the memory gate, wherein the elevation difference is greater than ten percent of a height of the select gate.

10. The method of claim 8 , wherein the operation of replacing the dummy gate with the metal gate forms the at least one logic device having a high-k metal gate structure.

11. The method of claim 8 , wherein the operation of polishing the dielectric layer comprises polishing the dielectric layer using a chemical mechanical polishing process.

12. The method of claim 8 , wherein the operation of forming the split gate memory device comprises forming an intermediate structure between the memory gate and the select gate, wherein the intermediate structure comprises a bottom layer, a trap layer and a top layer stacked in sequence.

13. The method of claim 8 , wherein the operation of forming the split gate memory device comprises forming the select gate from polysilicon.

14. The method of claim 13 , wherein the operation of forming the at least one logic device comprises forming the dummy gate from polysilicon.

15. The method of claim 8 , wherein the operation of forming the split gate memory device further comprises forming a hard mask on the select gate.

16. The method of claim 15 , wherein the operation of polishing the dielectric layer comprises polishing the hard mask.

17. A method for manufacturing a semiconductor device, comprising:

providing a substrate;

forming at least one logic device on the substrate, wherein the at least one logic device comprises a dummy gate;

forming a split gate memory device on the substrate, wherein the split gate memory device comprises a memory gate and a select gate adjacent to and electrically isolated with each other, the select gate has a flat top surface, and the memory gate has an inclined top surface;

forming a dielectric layer to cover the at least one logic device and the split gate memory device;

polishing the dielectric layer to expose a top of the select gate and a top of the dummy gate, wherein after the dielectric layer is polished, the top of the select gate is higher than a top of the memory gate, and an elevation difference between the top of the select gate and the top of the memory gate is greater than ten percent of a height of the select gate;

removing the dummy gate to form a recess in the at least one logic device;

forming a metal layer filling the recess and covering the dielectric layer, the split gate memory device and the at least one logic device; and

polishing the metal layer to expose the top of the select gate.

18. The method of claim 17 , wherein the operation of polishing the metal layer comprises polishing the metal layer using a chemical mechanical polishing process.

19. The method of claim 17 , wherein after the operation of polishing the dielectric layer is completed, a top surface of the dielectric layer and the flat top surface of the select gate are coplanar, and the elevation of the select gate is higher than the elevation of the memory gate.