Patent US5023196A successfully refreshed from Google Patents.
US5023196A
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Method for forming a MOSFET with substrate source contact
Assignee: Motorola Solutions Inc
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Filing: 1990-01-29
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Granted: 1991-06-11
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Expires: 2010-01-29
Abstract
Abstract A MOSFET having a back-side source contact and top-side gate and drain contacts is provided by a structure comprising superposed N + , N-,P-, N + regions arranged between top and bottom surfaces of the semiconductor die. In a preferred implementation, two trenches are etched from the top surface to the P-, N + interface. A buried P-, N + short is provided in one trench and a gate dielectric and gate electrode are provided over the sidewall P- region exposed in the other trench. This creates a vertical MOSFET in which the N + substrate forms the source region shorted to the P- body region in which the channel is created by the gate. Superior performance is obtained in RF grounded-source circuit applications.
Inventors
- 👤 Robert J. Johnsen
- 👤 Paul W. Sanders
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 23:10
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/60; H10D30/64; H10D30/66; H10D30/668; H10D10/00; H10D10/40; H10D30/01; H10D30/021; H10D30/025; H10D30/664; H10D62/00; H10D62/10; H10D62/17; H10D62/393; H10D64/00; H10D64/20; H10D84/00; H10D84/01; H10D84/0123; H10D84/0126; H10D84/0128; H10D84/0144; H10D84/0147; H10W; H10W20/00; H10W20/01; H10W20/021; H10D64/27; H10D64/311; H10D64/411; H10D64/511; H10D64/514; H10D64/516; Y; Y10; Y10S; Y10S148/00; Y10S148/168
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
170 words
A method for forming a semiconductor device comprising: providing a semiconductor substrate having a first region of a first type and conductivity extending to a first surface, a second region of the first type and a lower second conductivity underlying the first region, a third region of a second type opposite the first type and a third conductivity underlying the second region, and a fourth region of the first type and a fourth conductivity underlying the third region and extending to a second, opposite surface; forming a cavity extending into the substrate from the first surface, wherein first and second portions of the third region are exposed, respectively, on sides of the cavity and a first portion of the fourth region is also exposed in the cavity; and then in either order, (i) forming a gate oxide on the first portion of the third region, and (ii) forming a nonrectifying connection between the first portion of the fourth region and the second portion of the third region in the cavity.
Claim 2
Independent Claim
170 words
A method for forming a semiconductor device comprising: providing a semiconductor substrate having a first region of a first type and conductivity extending to a first surface, a second region of the first type and a lower second conductivity underlying the first region, a third region of a second type opposite the first type and a third conductivity underlying the second region, and a fourth region of the first type and a fourth conductivity underlying the third region and extending to a second, opposite surface; forming a cavity extending into the substrate from the first surface, wherein first and second portions of the third region are exposed, respectively, on sides of the cavity and a first portion of the fourth region is also exposed in the cavity; and then in either order, (i) forming a gate oxide on the first portion of the third region, and (ii) forming a nonrectifying connection between the first portion of the fourth region and the second portion of the third region in the cavity.
Claim 3
Dependent Claim
38 words
The method of claim 1 further comprising forming a gate electrode on the gate oxide, a source electrode contacting the fourth region on the second surface and a drain electrode contacting the first region on the first surface.
Claim 4
Dependent Claim
60 words
The method of claim 1 wherein the step of forming the cavity comprises, (i) initially etching the cavity by a first etch procedure to a first depth extending at least into the second region but not into the fourth region, and (ii) thereafter further etching the cavity by a second, different etch procedure to extend substantially to the fourth region.
Claim 5
Dependent Claim
22 words
The method of claim 3 wherein the initially etching step comprises anisotropic etching and the further etching step comprises orientation selective etching.
Claim 6
Independent Claim
91 words
A method for forming a semiconductor device, comprising: forming a semiconductor substrate having superposed , regions of conductivity and type represented by A + /A/B/A + where A=N or P type and B=the opposite type, extending between opposed top and bottom surfaces, respectively; forming a cavity extending from the top surface substantially through the A + /A/B regions; and forming, in a first portion of the cavity, a buried ohmic contact between the B/A + regions and, in a second portion of the cavity, a gate oxide on the B region.
Claim 7
Independent Claim
91 words
A method for forming a semiconductor device, comprising: forming a semiconductor substrate having superposed , regions of conductivity and type represented by A + /A/B/A + where A=N or P type and B=the opposite type, extending between opposed top and bottom surfaces, respectively; forming a cavity extending from the top surface substantially through the A + /A/B regions; and forming, in a first portion of the cavity, a buried ohmic contact between the B/A + regions and, in a second portion of the cavity, a gate oxide on the B region.
Claim 8
Dependent Claim
17 words
The method of claim 5 further comprising refilling the portion of the cavity over the ohmic contact.
Claim 9
Dependent Claim
35 words
The method of claim 6 further comprising forming a gate electrode on the gate oxide and a source contact to the bottom A + region and a drain contact to the top A + region.
Claim 10
Dependent Claim
31 words
The method of claim 5 wherein the the step of forming a buried ohmic contact comprises forming a metal or intermetallic contact to the B/A + regions exposed in the cavity.
Claim 11
Dependent Claim
34 words
The method of claim 8 wherein the buried ohmic contact is formed by selective deposition of a metal followed by a heating step to form a reaction product of the metal with the semiconductor.
Claim 12
Dependent Claim
16 words
The method of claim 4 further comprising providing a dielectric isolation wall laterally surrounding the cavity.
References Cited (Backward Citations)
US4398339A
Cited
JPS5457871A
Cited
GB2034114A
Cited
US4374455A
Cited
JPS5683944A
Cited
FR2487583A1
Cited
US4738936A
Cited
JPS60175457A
Cited
JPS60182774A
Cited
US4683643A
Cited
US4824793A
Cited
US4797373A
Cited
US4694561A
Cited
US4713678A
Cited
US4767722A
Cited
US4859621A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1994-06-10 | 1994-12-10 | 1995-06-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-06-10 | 1998-12-10 | 1999-06-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-06-10 | 2002-12-10 | 2003-06-11 | $7700.00 | Window Closed / Lapsed |