Trench mosfet with body region having concave-arc shape

• US 20110248340A1
• Filed: 04/07/2010
• Published: 10/13/2011
• Est. Priority Date: 04/07/2010
• Status: Active Grant

• Current Assignee: Force Mos Technology Co., Ltd.
• Original Assignee: Force Mos Technology Co., Ltd.
• Inventors: Hsieh, Fu-Yuan
• Granted Patent: US 8,378,392 B2
• Time in Patent Office: Days
• US Class Current: 257/334
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/1095 Body region, i.e. base region, of DMOS transistors or IGBTs cell layout H01L29/0696
• 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 29/7813 with trench gate electrode, e.g. UMOS transistors trench gate electrodes per se H01L29/4236

Abstract

A trench Metal Oxide Semiconductor Field Effect Transistor with improved body region structures is disclosed. By forming the inventive body region structures with concave-arc shape with respect to epitaxial layer, a wider interfaced area between the body region and the epitaxial layer is achieved, thus increasing capacitance between drain and source Cds. Moreover, the invention further comprises a Cds enhancement doped region interfaced with said body region having higher doping concentration than the epitaxial layer to further enhancing Cds without significantly impact breakdown voltage.

Claims

1. A trench MOSFET (Metal Oxide Semiconductor Field Effect Transistor) comprising:

a substrate of a first conductivity doping type;

an epitaxial layer of said first conductivity doping type over said substrate;

a plurality of trenched gates;

a plurality of source regions of said first conductivity doping type surrounding top portion of said trenched gates, said source regions have higher doping concentration than said substrate;

a plurality of body regions of a second conductivity doping type encompassing said source regions, said body regions have concave-arc shape with respect to top surface of said epitaxial layer;

a plurality of trenched source-body contacts; and

a plurality of body ohmic contact doped regions of said second conductivity doping type surrounding at least bottoms of said trenched source-body contacts.

2. The trench MOSFET of claim 1 further comprising a plurality of Cds enhancement doped regions of said first conductivity doping type interfaced with said body regions, said Cds enhancement doped regions are formed under said body regions and have higher doping concentration than said epitaxial layer.

3. The trench MOSFET of claim 2, wherein said Cds enhancement doped regions are not touching to said body ohmic contact doped regions.

4. The trench MOSFET of claim 2, wherein said Cds enhancement doped regions are touching to said body ohmic contact doped regions.

5. The trench MOSFET of claim 1, wherein said trenched gates are filled with doped poly-silicon padded by a gate oxide layer.

6. The trench MOSFET of claim 2, wherein said Cds enhancement doped regions are formed by ion implantation of Phosphorus through region of said trenched source-body contacts.

7. The trench MOSFET of claim 1, wherein said first conductivity doping type is N type, and said second conductivity doping type is P type for N-channel trench MOSFET.

8. The trench MOSFET of claim 1, wherein said first conductivity doping type is P type, and said second conductivity doping type is N type for P-Channel trench MOSFET.

9. The trench MOSFET of claim 1, wherein said trenched source-body contacts have vertical shape sidewalls, tapered shape sidewalls or combination of vertical and tapered shape sidewalls in said source regions and said body regions.

10. The trench MOSFET of claim 1, wherein said body ohmic contact doped regions surround bottom and sidewall of said trenched source-body contacts in said body regions.

11. The trench MOSFET of claim 1, wherein said body ohmic contact doped regions surround only bottom of said trenched source-body contacts in said body region.

12. The trench MOSFET of claim 5, wherein said doped poly-silicon layer protrudes out from top surface of said source regions and at least a portion of said doped poly-silicon is positioned higher than top surface of said source regions.

13. The trench MOSFET of claim 5, wherein top surface of said doped poly-silicon layer is not higher than top surface of said source regions.