Structure and method for forming trench-gate field effect transistor with source plug
A field effect transistor includes a gate trench extending into a semiconductor region. The gate trench has a recessed gate electrode disposed therein. A source region in the semiconductor region flanks each side of the gate trench. A conductive material fills an upper portion of the gate trench so as to make electrical contact with the source regions along upper sidewalls of the gate trench. The conductive material is insulated from the recessed gate electrode.
1. A field effect transistor comprising:
a gate trench extending into a semiconductor region, the gate trench having a recessed gate electrode disposed therein;
a first source region and a second source region disposed in the semiconductor region, the first source region and the second source region being respectively disposed on a first side and a second side of the gate trench; and
a conductive material disposed in an upper portion of the gate trench and in electrical contact with the first source region and with the second source region along an upper portion of a sidewall of the gate trench, the conductive material being insulated from the recessed gate electrode and having a top surface substantially coplanar with respective top surfaces of the first source region and the second source region.
2. The field effect transistor of claim 1 further comprising:
a body region disposed in the semiconductor region, the body region having a conductivity type opposite a conductivity type of the first source region and opposite a conductivity type of the second source region;
at least one conductive shield electrode disposed in the gate trench beneath the recessed gate electrode, the recessed gate electrode being insulated from the at least one conductive shield electrode;
a shield dielectric layer configured to insulate the at least one conductive shield electrode from the semiconductor region; and
a gate dielectric layer configured to insulate the gate electrode from the body region.
3. The field effect transistor of claim 2 wherein the semiconductor region includes a drift region disposed on a substrate, and the at least one conductive shield electrode has a bottom surface that is at a depth below a bottom depth of the drift region.
4. The field effect transistor of claim 1 wherein the conductive material includes polysilicon.
5. The field effect transistor of claim 1 wherein the semiconductor region includes a drift region disposed on a substrate, the drift region having a same conductivity type as the first source region and as the second source region.
6. The field effect transistor of claim 5 wherein the gate trench extends through the drift region and terminates within the substrate.
7. The field effect transistor of claim 5 wherein the gate trench extends into and terminates within the drift region.
8. The field effect transistor of claim 1 further comprising a top-side metal contacting the first source region, the second source region and the conductive material.
9. The field effect transistor of claim 1 wherein the first source region and the second source region have a vertical length extending along the sidewall of the gate trench and a lateral width extending perpendicular to the vertical length, the vertical length being greater than the lateral width.
10. The field effect transistor of claim 1 further comprising:
a shield dielectric disposed on a bottom surface of the gate trench and a lower portion of the sidewall of the gate trench, the shield dielectric being flared under a body region of the field effect transistor; and
a conductive shield electrode disposed within the shield dielectric in the gate trench.
11. A field effect transistor comprising:
a semiconductor region;
a gate trench extending into the semiconductor region;
a recessed gate electrode disposed within the gate trench;
a first source region and a second source region disposed in the semiconductor region, the first source region and the second source region being respectively disposed on a first side and a second side of the gate trench;
a dielectric layer disposed on the recessed gate electrode; and
a conductive material disposed on the dielectric layer and disposed in an upper portion of the gate trench, the conductive material making electrical contact with the first source region and with the second source region along an upper portion of a sidewall of the gate trench, the conductive material having a top surface substantially coplanar with respective top surfaces of the first source region and the second source region.
12. A field effect transistor comprising:
a semiconductor region;
a gate trench extending into the semiconductor region;
a recessed gate electrode disposed within the gate trench;
a source region disposed in the semiconductor region, the source region being disposed on a sidewall of the gate trench;
a dielectric layer disposed on the recessed gate electrode; and
a conductive material disposed on the dielectric layer and disposed in an upper portion of the gate trench, the conductive material making electrical contact with the source region along an upper portion of the sidewall of the gate trench, the conductive material having a top surface substantially coplanar with a top surface of the source region.
13. The field effect transistor of claim 12 further comprising a gate dielectric disposed on the sidewall of the gate trench, the gate dielectric being configured to insulate the recessed gate electrode from the semiconductor region.
14. The field effect transistor of claim 12 further comprising:
a shield dielectric disposed on a bottom surface of the gate trench and a lower portion of the sidewall of the gate trench, the shield dielectric being flared under a body region of the field effect transistor;
a conductive shield electrode disposed within the shield dielectric in the gate trench; and
an interpoly dielectric disposed on the conductive shield electrode, the interpoly dielectric being configured to insulate the conductive shield electrode from the recessed gate electrode.
15. The field effect transistor of claim 14 wherein the conductive material and the conductive shield electrode both include polysilicon.
16. The field effect transistor of claim 12 further comprising a body region disposed in the semiconductor region, the body region having a conductivity type opposite a conductivity type of the source region.
17. The field effect transistor of claim 12 wherein the conductive material includes polysilicon.
18. The field effect transistor of claim 12 further comprising a source interconnect layer disposed on the source region and the conductive material.
19. The field effect transistor of claim 12 further comprising a drift region disposed in the semiconductor region, the drift region being disposed on a substrate and having a same conductivity as the source region.
20. The field effect transistor of claim 12 further comprising a shield dielectric disposed on a bottom surface of the gate trench and a lower portion of the sidewall of the gate trench, the shield dielectric being flared under a body region of the field effect transistor.