Field effect device with enhanced gate dielectric structure
View Patent ↗A vertically oriented field effect device has a body and an enhance gate structure. The body includes a JFET (junction field effect transistor) region disposed between junction implants that extend into the body from a top surface of the body. The gate structure includes a supplemental gate dielectric, a primary gate dielectric, and a gate contact. The supplemental gate dielectric is formed over the top surface of the body above the JFET region, such that the supplemental dielectric is separated from the junction implants by a gap. The primary gate dielectric is formed over the supplemental gate dielectric, above the gap over the top surface of the body, and over at least a portion of the junction implants. The gate contact is formed over the primary gate dielectric.
1. A vertically oriented field effect device comprising:
a body comprising a junction gate field effect transistor (JFET) region disposed between junction implants that extend into the body from a top surface of the body;
a supplemental gate dielectric formed over the top surface of the body above the JFET region such that the supplemental gate dielectric is separated from the junction implants by a gap;
a primary gate dielectric formed over the supplemental gate dielectric, above the gap over the top surface of the body, and over at least a portion of the junction implants; and
a gate contact formed over the primary gate dielectric.
2. The field effect device of claim 1 wherein the top surface of the body is substantially planar over the JFET region and the junction implants.
3. The field effect device of claim 2 further comprising source contacts formed over the junction implants, wherein the source contacts are spaced apart from the gate contact and reside on a plane on which the supplemental gate dielectric resides.
4. The field effect device of claim 1 wherein a trench is formed into the JFET region from the top surface and the supplemental gate dielectric is formed in the trench, which is separated from the junction implants by the gap.
5. The field effect device of claim 4 further comprising source contacts formed over the junction implants, wherein the source contacts are spaced apart from the gate contact and reside on a different plane than a plane on which the supplemental gate dielectric resides.
6. The field effect device of claim 5 wherein side walls of the trench form an acute angle relative to the top surface.
7. The field effect device of claim 1 wherein side walls of the supplemental gate dielectric form an acute angle relative to the top surface.
8. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from a first dielectric material, and the primary gate dielectric is also formed from the first dielectric material.
9. The field effect device of claim 8 wherein the first dielectric material is silicon dioxide.
10. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from silicon dioxide.
11. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from at least one of aluminum oxide and magnesium oxide.
12. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from a first dielectric material, and the primary gate dielectric is formed from a second dielectric material, which is different than the first dielectric material.
13. The field effect device of claim 12 wherein the first dielectric material is at least one of aluminum oxide and magnesium oxide.
14. The field effect device of claim 13 wherein the second dielectric material is silicon dioxide.
15. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from a first material, the JFET region is formed from a second material, and the first material has a bandgap that is higher than that of the second material.
16. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from a first material, the JFET region is formed from a second material, and the first material has a bandgap that is at least 1.5 times that of the second material.
17. The field effect device of claim 1 wherein the supplemental gate dielectric is formed from a first material, the JFET region is formed from a second material, and the first material has a bandgap that is at least two times that of the second material.
18. The field effect device of claim 1 wherein the supplemental gate dielectric is an annealed dielectric material.
19. The field effect device of claim 1 further comprising a drain contact formed over a bottom surface of the body.
20. The field effect device of claim 19 further comprising source contacts formed over the junction implants, wherein the source contacts are spaced apart from the gate contact.
21. A vertically oriented field effect device comprising:
a body comprising a junction gate field effect transistor (JFET) region disposed between junction implants that extend into the body from a top surface of the body;
a supplemental gate dielectric formed on the top surface of the body over the JFET region such that the supplemental gate dielectric is separated from the junction implants by a gap;
a primary gate dielectric formed over the supplemental gate dielectric, above the gap on the top surface of the body, and over at least a portion of the junction implants;
a gate contact formed over the primary gate dielectric; and
a drain contact formed over a bottom surface of the body, wherein:
the supplemental gate dielectric is formed from a first material, the JFET region is formed from a second material, and the first material has a bandgap that is higher than that of the second material; and
the supplemental gate dielectric is formed from a first dielectric material, and the primary gate dielectric is formed from a second dielectric material, which is different than the first dielectric material.
22. The field effect device of claim 21 wherein the first material has a bandgap that is at least 1.5 times that of the second material.
23. The field effect device of claim 21 wherein the second material is silicon carbide.
24. The field effect device of claim 23 wherein the second dielectric material is silicon dioxide.
25. A method for forming a vertically oriented field effect device comprising:
providing a body comprising a junction gate field effect transistor (JFET) region disposed between junction implants that extend into the body from a top surface of the body;
forming a supplemental gate dielectric over the top surface of the body above the JFET region such that the supplemental gate dielectric is separated from the junction implants by a gap;
forming a primary gate dielectric over the supplemental gate dielectric, above the gap over the top surface of the body, and over at least a portion of the junction implants; and
forming a gate contact over the primary gate dielectric.
26. The method of claim 25 further comprising, prior to forming the primary gate dielectric, annealing the supplemental gate dielectric.
27. The method of claim 26 wherein the top surface of the body is substantially planar over the JFET region and the junction implants.
28. The method of claim 27 further comprising forming source contacts over the junction implants, wherein the source contacts are spaced apart from the gate contact and reside on a plane on which the supplemental gate dielectric resides.
29. The method of claim 25 further comprising forming a trench that extends into the JFET region from the top surface prior to forming the supplemental gate dielectric, wherein the supplemental gate dielectric is subsequently formed in the trench, which is separated from the junction implants by the gap.