High-mobility trench MOSFETs

• US 8,853,772 B2
• Filed: 07/22/2011
• Issued: 10/07/2014
• Est. Priority Date: 11/01/2007
• Status: Active Grant

• Current Assignee: Alpha & Omega Semiconductor, Ltd.
• Original Assignee: Alpha & Omega Semiconductor, Ltd.
• Inventors: Hbert, Franois
• Primary Examiner(s): Vu, David
• Application Number:
  US13/189,332
• Publication Number:
  US 20110278665A1
• Time in Patent Office: 1,173 Days
• Field of Search: 438/212, 438/268, 438/269, 438/270, 438/271, 438/272, 257328-331, 257/335, 257/339, 257/341, 257/E21.418, 257/E29.256, 257/E29.066, 257/E29.027
• US Class Current: 257/330
• CPC Class Codes: H01L 29/1054 with a variation of the composition, e.g. channel with strained layer for increasing the mobility
• CPC Class Codes: H01L 29/165 in different semiconductor regions , e.g. heterojunctions
• CPC Class Codes: H01L 29/4236 within a trench, e.g. trench gate electrode, groove gate electrode
• CPC Class Codes: H01L 29/42368 the thickness being non-uniform
• CPC Class Codes: H01L 29/456 on silicon
• CPC Class Codes: H01L 29/66734 with a step of recessing the gate electrode, e.g. to form a trench gate electrode
• CPC Class Codes: H01L 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236
• CPC Class Codes: H01L 29/7848 the means being located in the source/drain region, e.g. SiGe source and drain

Abstract

High-mobility vertical trench DMOSFETs and methods for manufacturing are disclosed. A source region, a drain region or a channel region of a high-mobility vertical trench DMOSFET may comprise silicon germanium (SiGe) that increases the mobility of the charge carriers in the channel region. In some embodiments the channel region may be strained to increase channel charge carriers mobility.

Claims

1. A high-mobility vertical trench DMOS, comprising:

a trenched gate formed in a trench in a semiconductor layer;

a top source region disposed next to the trenched gate;

a bottom drain region disposed below the bottom of the trenched gate; and

a channel region proximate to a sidewall of the trenched gate between the source and drain regions

wherein the channel region comprises SiGe of an opposite charge carrier type to a charge carrier type of the source region, wherein the SiGe is configured to increase the mobility of charge carriers in the channel region, wherein the SiGe is disposed on a sidewall of the trench but not on a bottom of the trench and not on a surface of the semiconductor layer, and

wherein a surface of the SiGe facing towards a center of the trench is in contact with a gate oxide layer.

2. A high-mobility vertical trench DMOS, comprising:

a trenched gate, formed in a trench in a semiconductor layer;

a top source region disposed next to the trenched gate;

a bottom drain region disposed below the bottom of the trenched gate; and

a channel region proximate to a sidewall of the trench between the source and drain regions,

wherein the channel region is not formed on a bottom of the trench and not formed on a surface of the semiconductor layer, and wherein a surface of the channel region facing towards a center of the trench is in contact with a gate oxide layer;

wherein the channel region is strained to increase channel charge carriers mobility.

3. The high-mobility vertical trench DMOS of claim 2 wherein the channel region comprises SiGe.

4. The high-mobility vertical trench DMOS of claim 3 wherein the channel region includes P-type SiGe.

5. The high-mobility vertical trench DMOS of claim 4, wherein the drain region comprises SiGe.

6. The high-mobility vertical trench DMOS of claim 5, wherein the drain region includes N-type SiGe.

7. The high-mobility vertical trench DMOS of claim 2, wherein the source region comprises SiGe.

8. The high-mobility vertical trench DMOS of claim 7, wherein the source region includes an N+ strained SiGe source.

9. The high-mobility vertical trench DMOS of claim 8, wherein the drain region comprises SiGe.

10. The high-mobility vertical trench DMOS of claim 9, wherein the drain region includes N-type SiGe.