Claims
- 1. A process of fabricating a trench MIS device comprising;
providing a substrate of a first conductivity type; forming a first epitaxial layer on the substrate, the first epitaxial layer being doped with a dopant of the first conductivity type to a doping concentration that is less than the doping concentration of the substrate; forming a second epitaxial layer on the first epitaxial layer, the second epitaxial layer being generally of a second conductivity type; forming a trench in the second epitaxial layer; forming sidewall spacers in the trench; implanting a dopant of the first conductivity type between the sidewall spacers and through a bottom of the trench; forming a bottom insulating layer on the bottom of the trench between the sidewall spacers; removing the sidewall spacers; forming a gate insulating layer on a sidewall of the trench, the gate insulating layer being thinner than the bottom insulating layer; and introducing a conductive material into the trench.
- 2. The process of claim 1 wherein forming sidewall spacers comprises depositing an insulating layer conformally in the trench and directionally etching the insulating layer so as to remove a portion of the insulating layer at a bottom of the trench, thereby leaving the sidewall spacers adjacent the walls of the trench.
- 3. The process of claim 2 wherein the insulating layer comprises nitride.
- 4. The process of claim 1 wherein implanting a dopant of the first conductivity type comprises implanting a dopant at a dose and energy such that following the implant and with substantially no thermal diffusion the dopant extends from the bottom of the trench to the first epitaxial layer.
- 5. The process of claim 1 wherein implanting a dopant of the first conductivity type comprises implanting the dopant at a dose and energy such that following the implant the dopant forms a region of the first conductivity type located below the bottom of the trench and not extending to the first epitaxial layer, the process further comprising heating the first epitaxial layer so as to diffuse the dopant downward, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 6. The process of claim 1 wherein implanting a dopant of the first conductivity type comprises implanting the dopant at a dose and energy such that following the implant the dopant forms a deep layer substantially separated from the trench, the process further comprising heating the first epitaxial layer so as to diffuse the dopant upward, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 7. The process of claim 1 wherein implanting a dopant of the first conductivity type comprises:
implanting a first portion of the dopant at a dose and energy such that following the implant the first portion of dopant forms a region of the first conductivity type located below the bottom of the trench and not extending to the first epitaxial layer; and implanting a second portion of the dopant at a dose and energy such that following the implant the second portion of the dopant forms a deep layer substantially separated from the trench; the process further comprising: heating the first epitaxial layer so as to diffuse the first portion of dopant downward and to diffuse the second portion of dopant upward such that the first and second portions merge, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 8. The process of claim 1 wherein implanting a dopant of the first conductivity type comprises implanting at least three portions of the dopant at different energies, respectively, so as to form a stack of contiguous regions of the first conductivity type, the stack forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 9. The process of any one of claims 1 through 8 wherein forming a bottom insulating layer comprises depositing a layer and etching the layer to form the bottom insulating layer.
- 10. The process of claim 9 wherein depositing a layer comprises depositing an oxide layer.
- 11. The process of claim 10 wherein depositing a layer comprises depositing a layer by chemical vapor deposition.
- 12. The process of claim 9 wherein the bottom insulating layer is a low-temperature oxide layer.
- 13. The process of claim 9 wherein depositing a layer comprises depositing a glass layer.
- 14. The process of any one of claims 1 through 8 wherein forming a bottom insulating layer comprises thermally growing an oxide layer on the bottom of the trench.
- 15. The process of any one of claims 1 through 8 wherein forming a bottom insulating layer comprises depositing a material that deposits preferentially on the bottom of the trench as compared with the sidewall spacers.
- 16-22. (canceled)
- 23. A process of fabricating a trench MIS device comprising;
providing a substrate of a first conductivity type; forming a first epitaxial layer on the substrate, the first epitaxial layer being doped with a dopant of the first conductivity type to a doping concentration that is less than the doping concentration of the substrate; forming a second epitaxial layer on the first epitaxial layer, the second epitaxial layer being generally of a second conductivity type; forming a trench in the second epitaxial layer; implanting a dopant of the first conductivity type through a bottom of the trench; forming a gate insulating layer on the bottom and a sidewall of the trench; and introducing a conductive material into the trench.
- 24. The process of claim 23 wherein implanting a dopant of the first conductivity type comprises implanting a dopant at a dose and energy such that following the implant and with substantially no thermal diffusion the dopant extends from the bottom of the trench to the first epitaxial layer.
- 25. The process of claim 23 wherein implanting a dopant of the first conductivity type comprises implanting the dopant at a dose and energy such that following the implant the dopant forms a region of the first conductivity type located below the bottom of the trench and not extending to the first epitaxial layer, the process further comprising heating the first epitaxial layer so as to diffuse the dopant downward, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 26. The process of claim 23 wherein implanting a dopant of the first conductivity type comprises implanting the dopant at a dose and energy such that following the implant the dopant forms a deep layer substantially separated from the trench, the process further comprising heating the first epitaxial layer so as to diffuse the dopant upward, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 27. The process of claim 23 wherein implanting a dopant of the first conductivity type comprises:
implanting a first portion of the dopant at a dose and energy such that following the implant the first portion of dopant forms a region of the first conductivity type located below the bottom of the trench and not extending to the first epitaxial layer; and implanting a second portion of the dopant at a dose and energy such that following the implant the second portion of the dopant forms a deep layer substantially separated from the trench; the process further comprising: heating the first epitaxial layer so as to diffuse the first portion of dopant downward and to diffuse the second portion of dopant upward such that the first and second portions merge, thereby forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 28. The process of claim 23 wherein implanting a dopant of the first conductivity type comprises implanting at least three portions of the dopant at different energies, respectively, so as to form a stack of contiguous regions of the first conductivity type, the stack forming a drain-drift region extending between the bottom of the trench and the first epitaxial layer.
- 29-32. (canceled)
Parent Case Info
[0001] This application is a continuation-in-part of application Ser. No. 10/326,311, which is a continuation-in-part of the following applications: application Ser. No. 10/317,568, filed Dec. 12, 2002, which is a continuation-in-part of application Ser. No. 09/898,652, filed Jul. 3, 2001; application Ser. No. 10/176,570, filed Jun. 21,2002; and application Ser. No. 10/106,812, filed Mar. 26, 2002, which is a continuation-in-part of application Ser. No. 09/927,143, filed Aug. 10, 2001. Each of the foregoing applications is incorporated herein by reference in its entirety.
Divisions (1)
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Number |
Date |
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Parent |
10454031 |
Jun 2003 |
US |
Child |
10872931 |
Jun 2004 |
US |
Continuation in Parts (6)
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Date |
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10326311 |
Dec 2002 |
US |
Child |
10454031 |
Jun 2003 |
US |
Parent |
10317568 |
Dec 2002 |
US |
Child |
10326311 |
Dec 2002 |
US |
Parent |
09898652 |
Jul 2001 |
US |
Child |
10317568 |
Dec 2002 |
US |
Parent |
10176570 |
Jun 2002 |
US |
Child |
10317568 |
Dec 2002 |
US |
Parent |
10106812 |
Mar 2002 |
US |
Child |
10317568 |
Dec 2002 |
US |
Parent |
09927143 |
Aug 2001 |
US |
Child |
10106812 |
Mar 2002 |
US |