US5981344A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Trench field effect transistor with reduced punch-through susceptibility and low RDSon
Assignee: Vishay Siliconix Inc
•
Filing: 1996-06-04
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Granted: 1999-11-09
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Expires: 2016-06-04
Abstract
Abstract To reduce susceptibility to punchthrough, the channel region of the P body region of a trench field effect transistor is formed in a layer of lightly doped epitaxial silicon. As a result, the channel region has less counterdoping from the background epitaxial silicon and has a greater net P type dopant concentration. Due to the higher net dopant concentration of the P body region, the depletion regions on either side of the P body region expand less far inward through the P body region at a given voltage, thereby rendering the transistor less susceptible to source-to-drain punchthrough. To maintain a low R DSon , the relatively high conductivity of an accumulation region formed along a sidewall of the trench of the transistor when the transistor is on is used to form a conductive path from the channel region to an underlying relatively highly conductive layer upon which the lightly doped epitaxial layer is formed. This underlying relatively highly conductive layer may, for example, be either substrate or a more highly doped epitaxial silicon layer.
Inventors
- 👤 Fwu-Iuan Hshieh
- 👤 Mike F. Chang
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:13
CPC Classifications
H; H10; H10D; H10D30/00; H10D30/60; H10D30/64; H10D30/66; H10D30/01; H10D30/021; H10D30/028; H10D30/0291; H10D30/63; H10D30/668; H10D62/00; H10D62/10; H10D62/13; H10D62/149; H10D62/151; H10D62/156; H10D62/157; H10D64/00; H10D64/20; H10D64/27; H10D64/311; H10D64/411; H10D64/511; H10D64/512; H10D64/513
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
189 words
A method comprising: providing a substrate of a first conductivity type; forming a lower layer of the first conductivity type on the substrate and having a doping level less than that of the substrate; forming an upper layer of the first conductivity type entirely overlying the lower layer and having a doping level less than that of the lower layer; defining a trench in the upper layer and lower layer and extending to within a predetermined distance of the substrate; filling the trench at least partially with a conductive gate electrode; forming a source region of the first conductivity type in the upper layer and extending to a principal surface of the upper layer and lying adjacent sidewalls of the trench; and forming a body region of a second conductivity type extending from the principal surface of the upper layer down to and into at least an upper portion of the lower layer and being spaced apart from a lower portion of the trench, wherein two spaced apart portions of the body region lying respectively on two sides of the trench define a lateral extent of the upper layer.
Claim 2
Independent Claim
189 words
A method comprising: providing a substrate of a first conductivity type; forming a lower layer of the first conductivity type on the substrate and having a doping level less than that of the substrate; forming an upper layer of the first conductivity type entirely overlying the lower layer and having a doping level less than that of the lower layer; defining a trench in the upper layer and lower layer and extending to within a predetermined distance of the substrate; filling the trench at least partially with a conductive gate electrode; forming a source region of the first conductivity type in the upper layer and extending to a principal surface of the upper layer and lying adjacent sidewalls of the trench; and forming a body region of a second conductivity type extending from the principal surface of the upper layer down to and into at least an upper portion of the lower layer and being spaced apart from a lower portion of the trench, wherein two spaced apart portions of the body region lying respectively on two sides of the trench define a lateral extent of the upper layer.
Claim 3
Dependent Claim
38 words
The method of claim 1, wherein the upper layer has a dopant concentration of first conductivity type dopants at least an order of magnitude lower than a dopant concentration of second conductivity type dopants in the body region.
Claim 4
Dependent Claim
27 words
The method of claim 1, wherein the body region has a net peak dopant concentration in the range of 3×10 16 to 9×10 16 /cm 3 .
Claim 5
Dependent Claim
16 words
The method of claim 1, wherein the upper and lower layers are each an epitaxial layer.
Claim 6
Dependent Claim
21 words
The method of claim 1, wherein no portion of the lower layer is laterally adjacent any portion of the upper layer.
Claim 7
Independent Claim
149 words
A method comprising: providing a substrate of a first conductivity type; forming a first layer of the first conductivity type on the substrate and having a doping level less than that of the substrate; defining a trench in the first layer and in the substrate; filling the trench at least partially with a conductive gate electrode; forming a source region of the first conductivity type in the first layer and extending to a principal surface of the first layer and lying adjacent sidewalls of the trench; and forming a body region of a second conductivity type extending from the principal surface of the first layer into at least an upper portion of the first layer and being spaced apart from a lower portion of the trench, wherein two portions of the body region lying respectively on two sides of the trench define a lateral extent of the first layer.
Claim 8
Independent Claim
149 words
A method comprising: providing a substrate of a first conductivity type; forming a first layer of the first conductivity type on the substrate and having a doping level less than that of the substrate; defining a trench in the first layer and in the substrate; filling the trench at least partially with a conductive gate electrode; forming a source region of the first conductivity type in the first layer and extending to a principal surface of the first layer and lying adjacent sidewalls of the trench; and forming a body region of a second conductivity type extending from the principal surface of the first layer into at least an upper portion of the first layer and being spaced apart from a lower portion of the trench, wherein two portions of the body region lying respectively on two sides of the trench define a lateral extent of the first layer.
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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) | 2002-11-08 | 2003-05-10 | 2003-11-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-11-08 | 2007-05-10 | 2007-11-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-11-08 | 2011-05-10 | 2011-11-09 | $7700.00 | Window Closed / Lapsed |