Trench-gate field effect transistor with channel enhancement region and methods of forming the same

• US 7,923,776 B2
• Filed: 02/02/2010
• Issued: 04/12/2011
• Est. Priority Date: 05/26/2005
• Status: Active Grant

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Kocon, Christopher Boguslaw, Yedinak, Joseph A., Dolny, Gary M., Sapp, Steven P., Kraft, Nathan L., Grebs, Thomas E., Ridley, Rodney S., Probst, Dean E., Yilmaz, Hamza, Calafut, Daniel, Marchant, Bruce D.
• Primary Examiner(s): PHAM, THANHHA S
• Application Number:
  US12/698,746
• Publication Number:
  US 20100258862A1
• Time in Patent Office: 434 Days
• Field of Search: 257/244, 257/330, 257/332, 257396-400, 257/E29.201
• US Class Current: 257/332
• CPC Class Codes: H01L 21/26586 characterised by the angle between the ion beam and the crystal planes or the main crystal surface
• CPC Class Codes: H01L 29/0878 Impurity concentration or distribution
• CPC Class Codes: H01L 29/402 Field plates
• CPC Class Codes: H01L 29/407 Recessed field plates, e.g. trench field plates, buried field plates
• 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 29/4236 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 29/66666 Vertical transistors H01L29/66712, H01L29/66742 take precedence
• CPC Class Codes: H01L 29/66727 with a step of recessing the source electrode
• 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 29/7806 the other device being a Schottky barrier diode
• CPC Class Codes: H01L 29/7811 with an edge termination structure guard regions per se H01L29/0619; field plates per se H01L29/402
• 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 29/7827 Vertical transistors H01L29/7802, H01L29/78642 take precedence
• CPC Class Codes: H01L 29/872 Schottky diodes

Abstract

A field effect transistor includes a body region of a first conductivity type in a semiconductor region of a second conductivity type. A gate trench extends through the body region and terminating within the semiconductor region. A source region of the second conductivity type extends in the body region adjacent the gate trench. The source region and an interface between the body region and the semiconductor region define a channel region therebetween which extends along the gate trench sidewall. A channel enhancement region of the second conductivity type is formed adjacent the gate trench. The channel enhancement region partially extends into a lower portion of the channel region to thereby reduce a resistance of the channel region.

Claims

1. A field effect transistor comprising:

a body region of a first conductivity type forming a PN junction with a semiconductor region of a second conductivity type;

a gate trench extending through the body region and terminating within the semiconductor region;

a source region of the second conductivity type adjacent the gate trench, the source region and an interface between the body region and the semiconductor region defining a channel region therebetween, the channel region extending along the gate trench sidewall; and

a channel enhancement region of the second conductivity type adjacent the gate trench, the channel enhancement region partially extending into a lower portion of the channel region to thereby reduce a resistance of the channel region.

2. The field effect transistor of claim 1 further comprising a gate electrode disposed in the gate trench, the channel enhancement region overlapping with the gate electrode along the trench gate sidewall.

3. The field effect transistor of claim 1 further comprising:

at least one conductive shield electrode disposed in the gate trench;

a gate electrode disposed in the gate trench over but insulated from the at least one conductive shield electrode;

a shield dielectric layer insulating the at least one conductive shield electrode from the semiconductor region; and

a gate dielectric layer insulating the gate electrode from the body region.

4. The field effect transistor of claim 1 wherein the semiconductor region includes a drift region of the second conductivity type extending over a substrate.

5. The field effect transistor of claim 4 wherein the gate trench extends through the drift region and terminates within the substrate.

6. The field effect transistor of claim 4 wherein the channel enhancement region partially extends into the body region and partially extends into the drift region.

7. The field effect transistor of claim 3 wherein the semiconductor region includes a drift region of the second conductivity type extending over a substrate, and the shield electrode vertically overlaps the drift region and the substrate.

13. The field effect transistor of claim 3 wherein the semiconductor region includes a drift region of the second conductivity type extending over a substrate, and each shield electrode vertically overlaps the drift region and the substrate.

8. A shielded gate field effect transistor comprising:

body regions of a first conductivity type extending in a semiconductor region of a second conductivity type;

gate trenches separated by the body regions;

at least one conductive shield electrode disposed in each gate trench;

a gate electrode disposed in each gate trench over but insulated from the at least one conductive shield electrode;

a shield dielectric layer insulating the at least one conductive shield electrode from the semiconductor region; and

a gate dielectric layer insulating each gate electrode from adjacent body regions;

source regions of the second conductivity type extending in the body region adjacent the gate trenches, each source region and an interface between the corresponding body region and the semiconductor region defining a channel region therebetween, each channel region extending along sidewall of the corresponding gate trench; and

a channel enhancement region of the second conductivity type adjacent each gate trench, the channel enhancement region partially extending into a lower portion of the corresponding channel region to thereby reduce a resistance of the channel region.

9. The field effect transistor of claim 8 wherein the channel enhancement region overlaps with a corresponding gate electrode along the corresponding trench gate sidewall.

10. The field effect transistor of claim 8 wherein the semiconductor region includes a drift region of the second conductivity type extending over a substrate.

11. The field effect transistor of claim 10 wherein the gate trenches extend through the drift region and terminate within the substrate.

12. The field effect transistor of claim 10 wherein each channel enhancement region partially extends into the corresponding body region and partially extends into the drift region.