Schottky diode and method for fabricating the same

1. A Schottky diode, comprising:

a substrate;

a first-type buried layer in the substrate;

a cathode region, comprising:

a high-voltage second-type lightly doped drain in the substrate;

a first-type well surrounding the high-voltage second-type lightly doped drain; and

a first-type doping region in the first-type well and surrounding the high-voltage second-type lightly doped drain;

an anode region surrounding the cathode region; and

a first-type guard ring surrounding the anode region and connected to the first-type buried layer.

2. The Schottky diode of claim 1 , further comprising a second-type buried layer between the first-type buried layer and the cathode region.

3. The Schottky diode of claim 2 , further comprising a high-voltage second-type well between the second-type buried layer, the first-type guard ring, the cathode region, and the anode region.

4. The Schottky diode of claim 1 , wherein the anode region comprises:

the high-voltage second-type lightly doped drain; and

a second-type doping region in the high-voltage second-type lightly doped drain.

5. The Schottky diode of claim 1 , wherein the first-type guard ring comprises:

a high-voltage deep first-type well;

a high-voltage first-type lightly doped drain in the high-voltage deep first-type well;

the first-type well in the high-voltage first-type lightly doped drain;

a first-type lightly doped drain in the first-type well; and

the first-type doping region in the first-type lightly doped drain.

6. The Schottky diode of claim 1 , further comprising a second-type guard ring surrounding the first-type guard ring, wherein the second-type guard ring comprises:

a high-voltage second-type well;

a second-type well in the high-voltage second-type well; and

a second-type doping region in the second-type well.

7. The Schottky diode of claim 1 , further comprising an isolation structure between the cathode region and the anode region, and between the anode region and the first-type guard ring.

8. The Schottky diode of claim 1 , further comprising a contact plug directly contacting the high-voltage second-type lightly doped drain.

9. The Schottky diode of claim 8 , wherein the contact plug comprises Ti and TiN.

10. The Schottky diode of claim 1 , wherein the first-type is n-type and second-type is p-type.

11. A method for fabricating Schottky diode, comprising:

providing a substrate;

forming a first-type buried layer in the substrate;

forming a first-type guard ring in the substrate, wherein the first-type guard ring contacts the first-type buried layer;

forming a cathode region in the substrate, wherein the cathode region comprises:

a high-voltage second-type lightly doped drain in the substrate;

a first-type well surrounding the high-voltage second-type lightly doped drain; and

a first-type doping region in the first-type well surrounding the high-voltage second-type lightly doped drain; and

forming an anode region between the cathode region and the first-type guard ring.

12. The method of claim 11 , further comprising forming a second-type buried layer between the first-type buried layer and the cathode region.

13. The method of claim 12 , further comprising forming a high-voltage second-type well between the second-type buried layer, the first-type guard ring, the cathode region, and the anode region.

14. The method of claim 11 , further comprising:

forming a high-voltage deep first-type well;

forming a high-voltage first-type lightly doped drain;

forming the first-type well;

forming a first-type lightly doped drain; and

forming the first-type doping region for forming the first-type guard ring.

15. The method of claim 11 , further comprising:

forming the high-voltage second-type lightly doped drain; and

forming a second-type doping region in the high-voltage second-type lightly doped drain for forming the anode region.

16. The method of claim 11 , further comprising:

forming a high-voltage second-type well in the substrate;

forming a second-type well in the high-voltage second-type well; and

forming a second-type doping region in the second-type well for forming a second-type guard ring surrounding the first-type guard ring.

17. The method of claim 11 , further comprising:

forming an isolation structure between the cathode region and the anode region, and between the anode region and the first-type guard ring.

18. The method of claim 11 , further comprising:

forming a dielectric layer on the substrate;

forming an opening in the dielectric layer to expose the high-voltage second-type lightly doped drain;

sputtering a first metal layer in the opening;

performing an anneal process;

depositing a second metal layer in the opening;

depositing a third metal layer in the opening; and

performing a planarizing process for forming a contact plug contacting the high-voltage second-type lightly doped drain.

19. The method of claim 18 , wherein the first metal layer comprises Ti or TiN, the second metal layer comprises TiN, and the third metal layer comprises W.

20. The method of claim 11 , wherein the first-type is n-type and the second-type is p-type.