EP0514060A2
Expired / Lapsed
EP
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DMOS transistor structure & method
Assignee: Vishay Siliconix Inc
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Filing: 1992-05-05
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Granted: —
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Expires: 2012-05-05
Abstract
Abstract An LDD lateral DMOS transistor is provided in a lightly-doped epitaxial layer of a first conductivity above a substrate of the same conductivity. A highly-doped buried layer of the first conductivity is provided under the LDD lateral DMOS transistor to relieve crowding of electrical equipotential distribution beneath the silicon surface. In one embodiment, a gate plate is provided above the gate and the gate-edge of the drift region. An optional N-well provides further flexibility to shape electric fields beneath the silicon surface. The buried layer can also reduce the electric field in a LDD lateral diode and improves cathode-to-anode reversed-recovery characteristics. <IMAGE>
Inventors
- 👤 Richard K. Williams
- 👤 Michael E. Cornell
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 11:00
CPC Classifications
H; H10; H10D; H10D62/00; H10D62/10; H10D62/17; H10D62/351; H10D62/357; H10D62/364; H10D30/00; H10D30/01; H10D30/021; H10D30/0221; H10D30/60; H10D30/601; H10D30/603; H10D84/00; H10D84/80; H10D84/82; H10D84/83; H10D84/835; H10D84/85; H10D84/856; H10D30/64; H10D30/65; H10D62/124; H10D62/126; H10D62/213; H10D62/221; H10D62/235; H10D62/299; H10D62/307; H10D64/00; H10D64/111; H10D64/20; H10D64/27; H10D64/311; H10D64/411; H10D64/511; H10D64/514; H10D64/516; Y; Y10; Y10S; Y10S148/00; Y10S148/126
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
194 words
A lateral DMOS transistor structure, comprising: an epitaxial layer of a first conductivity formed on one surface of a substrate of the first conductivity; a source region of a second conductivity formed in the epitaxial layer opposite the first conductivity; a body region of the first conductivity formed in the epitaxial layer adjacent the source region, a portion of the body region being exposed on the surface of the epitaxial layer; a drift region of the second conductivity formed in the epitaxial layer and spaced from the source and the body regions by an exposed portion of the epitaxial layer on the surface of the epitaxial layer away from the surface of the substrate, such that the exposed portion of the body region and the exposed portion of the epitaxial layer form a channel region between the source region and the drift region; a drain region of the second conductivity formed in the epitaxial layer adjacent the drift region away from the channel region; a gate region formed above the channel region; and a buried layer of the first conductivity having a portion located underneath the interface between the channel and the drift regions.
Claim 2
Dependent Claim
26 words
A structure as claimed in claim 1 having a gate plate located above the gate and extending over the interface between the channel and drift regions.
Claim 3
Dependent Claim
29 words
A structure as claimed in claim 1 or 2 having a drain plate located above the drain region and extending over the interface between the drift and drain regions.
Claim 4
Dependent Claim
18 words
A structure as claimed in claim 1, 2 or 3 which is substantially annular about the drain region.
Claim 5
Dependent Claim
179 words
A lateral DMOS transistor structure, comprising: an epitaxial layer of a first conductivity formed on one surface of a substrate of the first conductivity; a gate region above the epitaxial layer, the gate defining on the surface of the epitaxial layer a channel region underneath the gate; a source region of a second conductivity opposite the first conductivity in the epitaxial layer having a portion exposed on the surface of the epitaxial layer region adjacent the channel region; a body region of the first conductivity formed in the channel region in the epitaxial layer adjacent the source region; a drift region of the second conductivity formed in the epitaxial layer adjacent the channel region away from the body region; a drain region of the second conductivity formed in the epitaxial layer adjacent the drift region; an oxide region adjacent the drift region and located away from the interface between the channel region and the drift region; and a buried layer of the first conductivity having a portion located underneath the interface between the drift region and the oxide region.
Claim 6
Dependent Claim
25 words
A structure as claimed in claim 5 wherein the buried layer has a second portion located underneath the interface between the channel and drift regions.
Claim 7
Dependent Claim
55 words
A structure as claimed in claim 5 or 6 having a gate plate above the gate extending over the interface between the channel and the drift regions and extending along the boundary of the drift region to provide a portion of the gate plate above the interface between the oxide layer and the drift region.
Claim 8
Dependent Claim
26 words
A structure as claimed in any preceding claim having a deep diffusion region of the first conductivity in the epitaxial layer and adjacent the body region.
Claim 9
Dependent Claim
26 words
A structure as claimed in any preceding claim having a deep diffusion region of the second conductivity in the epitaxial layer and adjacent the drain region.
Claim 10
Dependent Claim
195 words
An LDD DMOS transistor structure, comprising: a buried layer of a first conductivity formed on a surface of a substrate of the first conductivity; an epitaxial layer of the first conductivity formed on the surface of the substrate; a drift region of a second conductivity formed in the epitaxial layer, a portion of the boundary of the drift region being located above the buried layer; an oxide layer formed above the drift region; a gate formed above the epitaxial layer such that the portion of the epitaxial layer underneath the gate is adjacent the portion of the boundary of the drift region, the portion of the epitaxial layer forming a channel region; a body region formed in the epitaxial layer and having a portion in the channel region exposed on the surface of the epitaxial layer, the exposed portion of the body region being located away from the drift region; a source region of the second conductivity formed in the epitaxial layer adjacent the channel region and the exposed portion of said body region; a drain region of the second conductivity formed in the epitaxial layer adjacent the drift region away from the channel region.
Claim 11
Dependent Claim
28 words
A structure as claimed in claim 10 having a deep diffusion region of the first conductivity in said epitaxial layer adjacent the body region and the buried layer.
Claim 12
Dependent Claim
30 words
A structure as claimed in claim 10 or 11 wherein the gate extends over the oxide region forming a gate plate above the interface between the channel and drift regions.
Claim 13
Dependent Claim
154 words
A self-isolated diode structure, comprising: a buried layer of a fist conductivity formed on one surface of a substrate of the first conductivity; an epitaxial layer of the first conductivity formed on the surface of said substrate; an oxide layer formed on top of the epitaxial layer, the oxide layer partially covering the epitaxial layer, and exposing first and second regions of the epitaxial layer, a portion of the boundary of the first region being located above the buried layer; a drift region of a second conductivity formed in the first region of the epitaxial layer adjacent the oxide layer at the potion of the boundary; a cathode region of the second conductivity formed in the first region of the epitaxial layer adjacent the drift region away from the portion of the boundary, and an anode region of the first conductivity formed in the second region of the epitaxial layer adjacent the oxide layer.
Claim 14
Dependent Claim
28 words
A structure as claimed in claim 13 having a deep diffusion region of the first conductivity in the epitaxial layer adjacent the anode region and the buried layer.
Claim 15
Dependent Claim
20 words
A structure as claimed in any preceding claim wherein the first conductivity is p-type and the second conductivity is n-type.
Claim 16
Independent Claim
170 words
A method of providing an LDD lateral DMOS transistor, comprising the steps of: providing a buried layer of a first conductivity on one surface of the substrate of the first conductivity; providing an epitaxial layer of the first conductivity above the surface of the substrate; providing a gate above the surface of the epitaxial layer, thereby defining a channel region underneath the gate on the surface of said epitaxial layer; providing a drift region of a second conductivity adjacent the channel region such that the interface between the channel and drift regions is located above the buried layer; providing a body region of the first conductivity having a portion exposed on the surface of the epitaxial layer in the channel region away from the drift region; and providing source and drain regions of the second conductivity in the epitaxial layer, the source region being adjacent the channel region and the exposed portion of the body region, and the drain region being adjacent the drift region away from the channel region.
Claim 17
Dependent Claim
28 words
A method as claimed in claim 16 having the step of providing a gate plate above the gate extending over the interface between the channel and drift regions.
Claim 18
Dependent Claim
31 words
A method as claimed in claim 16 or 17 having the step of providing a drain plate above the drain region extending over the interface between the drift and drain regions.
Claim 19
Dependent Claim
21 words
A method as claimed in claim 16, 17 or 18 wherein the transistor structure is substantially annular about the drain region.
Claim 20
Independent Claim
256 words
A method of providing an LDD lateral DMOS transistor, comprising the steps of: providing a buried layer of the first conductivity above one surface of a substrate of the first conductivity; providing an epitaxial layer of the first conductivity on the surface of the substrate; providing an oxide layer above the surface of the epitaxial layer, the oxide layer partially covering the surface of the epitaxial layer and exposing a region of the epitaxial layer; providing a gate above the region of the epitaxial layer away from the oxide layer, thereby defining underneath the gate in the region of the epitaxial layer a channel region, and such that a portion of the boundary of the channel region lies above a first portion of the buried layer; providing a drift region of a second conductivity at the surface of the epitaxial layer adjacent the portion of the boundary of the channel region and adjacent the oxide layer, such that the interface between the oxide layer and the drift region lies above a second portion of the buried layer; providing a body region in the epitaxial layer and having a portion of the body region exposed on the surface of the epitaxial layer in the channel region away from the drift region; and providing source and drain regions of the second conductivity at the surface of the epitaxial layer, the source region being adjacent the exposed portion of the body region, and the drain region located between the oxide layer and the channel region adjacent the drift region.
Claim 21
Dependent Claim
30 words
A method as claimed in claim 20 having the step of providing a gate plate above the gate and extending over the portion of the boundary of the channel region.
Claim 22
Dependent Claim
31 words
A method as claimed in claim 20 or 21 having the step of providing a drain plate above the drain and extending over the interface between the oxide and drift regions.
Claim 23
Independent Claim
31 words
A method as claimed in any one of claims 16-22 having the step of providing a deep diffusion region of the first conductivity in the epitaxial layer adjacent the body region.
Claim 24
Independent Claim
31 words
A method as claimed in any one of claims 16-23 having the step of providing a deep diffusion region of the second conductivity in the epitaxial layer adjacent the drain region.
Claim 25
Independent Claim
197 words
A method of providing an LDD DMOS transistor structure, comprising the steps of: providing a buried layer of a first conductivity on a surface of a substrate of the first conductivity; providing an epitaxial layer of the first conductivity on the surface of the substrate; providing a drift region of a second conductivity in the epitaxial layer, a portion of the boundary of the drift region being located above the buried layer; providing an oxide layer above the drift region; providing a gate above the epitaxial layer such that the portion of the epitaxial layer underneath the gate and adjacent the portion of the boundary of the drift region forms a channel region; providing a body region in the epitaxial layer, the body region having a portion exposed on the surface of the epitaxial layer in the channel region, the exposed portion of body region being located away from the drift region; and providing source and drain regions of the second conductivity, the source region being formed in the epitaxial layer adjacent the portion of the body region and the drain region being formed in the epitaxial layer adjacent the drift region away from the channel region.
Claim 26
Dependent Claim
32 words
A method as claimed in claim 25 having the step of providing a deep diffusion region of the first conductivity in the epitaxial layer adjacent the body region and the buried layer.
Claim 27
Dependent Claim
38 words
A method as claimed in claim 25 or 26 wherein the gate extends over the oxide region formed prior to the gate providing step, thereby forming a gate plate above the interface between the channel and drift regions.
Claim 28
Independent Claim
161 words
A method of providing a self-isolated diode structure, comprising the steps of: providing a buried layer of a first conductivity on one surface of a substrate of the first conductivity; providing an epitaxial layer of the first conductivity on the surface of the substrate; providing an oxide layer on top of the epitaxial layer, the oxide layer partially covering the epitaxial layer, and exposing first and second regions of the epitaxial layer, a portion of the boundary of the first region being located above the buried layer; providing a drift region of a second conductivity in the first region of the epitaxial layer adjacent the oxide region at said portion of the boundary; providing a cathode region of the second conductivity in the first region of the epitaxial layer adjacent the drift region away from said portion of the boundary; and providing an anode region of the first conductivity in the second region of the epitaxial layer adjacent the oxide region.
Claim 29
Dependent Claim
32 words
A method as claimed in claim 28 having the step of providing a deep diffusion region of the first conductivity in the epitaxial region adjacent the anode region and the buried layer.
References Cited (Backward Citations)
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