US5023196A
Expired / Lapsed
US
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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 19:24
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.
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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 |