Lateral RF MOS device with improved drain structure

• US 6,222,233 B1
• Filed: 10/04/1999
• Issued: 04/24/2001
• Est. Priority Date: 10/04/1999
• Status: Expired due to Term

• Current Assignee: Qorvo US, Inc. (Qorvo, Inc.)
• Original Assignee: Xemod, Inc. (Qorvo, Inc.)
• Inventors: D'Anna, Pablo Eugenio
• Primary Examiner(s): LOKE, STEVEN HO YIN
• Application Number:
  US09/410,934
• Time in Patent Office: 568 Days
• Field of Search: 257/343, 257/408, 257/409
• US Class Current: 257/343
• CPC Class Codes: H01L 29/0653 adjoining the input or output region of a field-effect device, e.g. the source or drain region
• CPC Class Codes: H01L 29/0847 of field-effect transistors with insulated gate H01L29/0653 takes precedence; with a passive supplementary region between source or drain and substrate related to punch-through, capacity or isolation phenomena H01L29/1079; with LDD or DDD structure H01L29/7833; for thin film transistors H01L29/78618
• CPC Class Codes: H01L 29/1087 characterised by the contact structure of the substrate region, e.g. for controlling or preventing bipolar effect
• CPC Class Codes: H01L 29/41766 with at least part of the source or drain electrode having contact below the semiconductor surface, e.g. the source or drain electrode formed at least partially in a groove or with inclusions of conductor inside the semiconductor H01L29/41733 - H01L29/41758 take precedence
• CPC Class Codes: H01L 29/7835 with asymmetrical source and drain regions, e.g. lateral high-voltage MISFETs with drain offset region, extended drain MISFETs

Abstract

The lateral RF MOS device having a conducive plug in the source region and an oxide plug in the drain region is disclosed. The oxide plug in the drain region reduces the drain-source capacitance, improves the matching ability to the outside circuitry, and results in a lateral RF MOS device having a wider BW, and an improved power efficiency than a prior art lateral RF MOS device. The oxide plug can comprise a shallow plug or a deep plug. The shallow oxide plug results in a lesser reduction in the drain-source capacitance but is relatively easy to fabricate. The deep oxide plug results in a higher reduction in the drain-source capacitance but is relatively difficult to fabricate.

Claims

1. A lateral RF MOS transistor structure comprising:

a semiconductor material of a first conductivity type, said semiconductor material having a first dopant concentration and a top surface;

a conductive gate overlying and insulated from said top surface of said semiconductor material;

a first region formed completely within said semiconductor material of said first conductivity type, said first region being of a second conductivity type and having a second dopant concentration to form an enhanced drain drift region of said RF MOS transistor structure;

a second region formed in said semiconductor material, said second region being of said second conductivity type and having a third dopant concentration greater than said second dopant concentration to form a drain region of said RF MOS transistor, said second region contacting said first region;

a third region formed in said semiconductor material, said third region being of said first conductivity type and having a fourth dopant concentration to form a body region of said RF MOS transistor structure, said fourth dopant concentration being greater than said first dopant concentration, said third region having a first end underlying said conductive gate, any remaining portion of said semiconductor material underlying said gate being of said first conductivity type;

a fourth region formed in said semiconductor material, said fourth region being of said second conductivity type and having a fifth dopant concentration to form a source region of said RF MOS transistor structure, said fourth region being located within said third region;

a fifth region formed in said semiconductor material, said fifth region being of said first conductivity type and having a sixth dopant concentration to form a contact enhancement region of said RF MOS transistor structure, said sixth dopant concentration being greater than said fourth dopant concentration of said third region, said fifth region being located within said third region;

a conductive plug region formed in said source region and said body region of said semiconductor material; and

an oxide region formed in said drain region of said RF MOS transistor.

2. The lateral RF MOS transistor structure of claim 1, wherein said oxide region comprises a shallow oxide plug region formed underneath a drain contact area, and wherein said shallow oxide plug region is located completely within said semiconductor material of said first conductivity type.

3. The lateral RF MOS transistor structure of claim 1, wherein said oxide region comprises a deep oxide plug region formed underneath a drain contact area, and wherein said deep oxide plug region separates a top or lateral surface of said drain region from a highly conductive substrate of said structure.

4. The lateral RF MOS transistor structure of claim 1, wherein said conductive plug region connects said source region and said body region of said semiconductor material to a backside of said structure.

5. The lateral RF MOS transistor structure of claim 1, wherein said conductive plug region connects a top or lateral surface of said source and a lateral surface of said body region of said semiconductor material to a highly conductive substrate of said structure.

6. The lateral RF MOS transistor structure of claim 1, wherein said first conductivity type is a P type.

7. The lateral RF MOS transistor structure of claim 1, wherein said conductive plug comprises a metal plug.

8. The lateral RF MOS transistor structure of claim 1, wherein said conductive plug comprises a silicided plug.

9. The lateral RF MOS transistor structure of claim 8, wherein said silicided plug comprises a tungsten silicided plug.

10. The lateral RF MOS transistor structure of claim 8, wherein said silicided plug comprises a titanium silicided plug.

11. The lateral RF MOS transistor structure of claim 8, wherein said silicided plug comprises a cobalt silicided plug.

12. The lateral RF MOS transistor structure of claim 8, wherein said silicided plug comprises a platinum silicided plug.

13. A lateral RF MOS transistor structure comprising:

a semiconductor material of a first conductivity type, said semiconductor material having a first dopant concentration and a top surface;

a conductive gate overlying and insulated from said top surface of said semiconductor material;

a first region formed completely within said semiconductor material of said first conductivity type, said first region being of a second conductivity type and having a second dopant concentration to form a first enhanced drain drift region of said RF MOS transistor structure;

a second region formed in said semiconductor material, said second region being of said second conductivity type and having a third dopant concentration higher than said second dopant concentration to form a second enhanced drain drift region of said RF MOS transistor, said second region contacting said first region;

a third region formed in said semiconductor material, said third region being of said second conductivity type and having a fourth dopant concentration greater than said second dopant concentration to form a drain region of said RF MOS transistor, said third region contacting said second region;

a fourth region formed in said semiconductor material, said fourth region being of said first conductivity type and having a fifth dopant concentration to form a body region of said RF MOS transistor structure, said fifth dopant concentration being greater than said first dopant concentration, said fourth region having a first end underlying said conductive gate, any remaining portion of said semiconductor material underlying said gate being of said first conductivity type;

a fifth region formed in said semiconductor material, said fifth region being of said second conductivity type and having a sixth dopant concentration to form a source region of said RF MOS transistor structure, said fifth region being located within said fourth region;

a sixth region formed in said semiconductor material, said sixth region being of said first conductivity type and having a seventh dopant concentration to form a contact enhancement region of said RF MOS transistor structure, said seventh dopant concentration being greater than said fifth dopant concentration of said fourth region, said sixth region being located within said fourth region;

a conductive plug region formed adjacent to said body region of said semiconductor material; and

an oxide region formed in said drain region of said RF MOS transistor.

14. The lateral RF MOS transistor structure of claim 13, wherein said oxide region comprises a shallow oxide plug region formed underneath a drain contact area, and wherein said shallow oxide plug region is located completely within said semiconductor material of said first conductivity type.

15. The lateral RF MOS transistor structure of claim 13, wherein said oxide region comprises a deep oxide plug region formed underneath a drain contact area, and wherein said deep oxide plug region separates a top or lateral surface of said drain region from a highly conductive substrate of said structure.

16. The lateral RF MOS transistor structure of claim 13, wherein said conductive plug region connects said source region and said body region of said semiconductor material to a backside of said structure.

17. The lateral RF MOS transistor structure of claim 13, wherein said conductive plug region connects a top or lateral surface of said source and a lateral surface of said body region of said semiconductor material to a highly conductive substrate of said structure.

18. The lateral RF MOS transistor structure of claim 13, wherein said first conductivity type is a P type.

19. The lateral RF MOS transistor structure of claim 13, wherein said conductive plug comprises a metal plug.

20. The lateral RF MOS transistor structure of claim 13, wherein said conductive plug comprises a silicided plug.

21. The lateral RF MOS transistor structure of claim 20, wherein said silicided plug comprises a tungsten silicided plug.

22. The lateral RF MOS transistor structure of claim 20, wherein said silicided plug comprises a titanium silicided plug.

23. The lateral RF MOS transistor structure of claim 20, wherein said silicided plug comprises a cobalt silicided plug.

24. The lateral RF MOS transistor structure of claim 20, wherein said silicided plug comprises a platinum silicided plug.