US4238758A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semiconductor gas sensor
Assignee: Suwa Seikosha KK
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Filing: 1978-12-08
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Granted: 1980-12-09
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Expires: 1998-12-08
Abstract
Abstract A metal-oxide-semiconductor transistor gas sensor including a gate oxide film of a dielectric material having a permittivity of more than about ten between a substrate and a gate is provided. The existence of a particular gas is detected by the change in threshold voltage of the transistor.
Inventors
- 👤 Shunji Suzuki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 05:11
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/26; G01N27/403; G01N27/414; G01N27/4141; G01N27/4143
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
161 words
A metal-oxide-semiconductor transistor gas sensor comprising: a semi-conductive substrate of given conductivity type; at least two spaced apart diffusion regions in said substrate, said diffusion regions formed from a dopant material having a conductivity opposite from said substrate; a field oxide film disposed on the surface of said substrate contacting at least a portion of the surface of each of said diffusion regions; a gate oxide film comprising an oxide semiconductor having a work-function dependent upon absorption of gas, said gate oxide film disposed on the surface of said substrate at the region free of said dopant material and contacting at least a portion of the remaining surface of each of said diffusion regions, said gate oxide film having a permittivity of more than 10; a gate disposed on said gate oxide film; and contact means for connecting said spaced apart diffusion regions and said gate electrode to external circuitry for detecting said charge in work-function of said gate oxide film.
Claim 2
Dependent Claim
161 words
A metal-oxide-semiconductor transistor gas sensor comprising: a semi-conductive substrate of given conductivity type; at least two spaced apart diffusion regions in said substrate, said diffusion regions formed from a dopant material having a conductivity opposite from said substrate; a field oxide film disposed on the surface of said substrate contacting at least a portion of the surface of each of said diffusion regions; a gate oxide film comprising an oxide semiconductor having a work-function dependent upon absorption of gas, said gate oxide film disposed on the surface of said substrate at the region free of said dopant material and contacting at least a portion of the remaining surface of each of said diffusion regions, said gate oxide film having a permittivity of more than 10; a gate disposed on said gate oxide film; and contact means for connecting said spaced apart diffusion regions and said gate electrode to external circuitry for detecting said charge in work-function of said gate oxide film.
Claim 3
Dependent Claim
44 words
The gas sensor of claim 1, wherein said contact means includes a metal electrode in contact with the surface of each said diffusion region free of oxide film for providing electrical connection to said diffusion regions and an electrode in contact with said gate.
Claim 4
Dependent Claim
36 words
The gas sensor of claim 1 for detecting hydrogen, wherein said gate is palladium and said gate oxide film is a dielectric film for providing a large change in threshold voltage in the presence of hydrogen.
Claim 5
Dependent Claim
21 words
The gas sensor of claim 3, wherein said dielectric film comprises titanium dioxide of permittivity of between about 70 and 85.
Claim 6
Dependent Claim
21 words
The gas sensor of claim 3, wherein said dielectric film is titanium dioxide-magnesium oxide of permittivity between about 18 and 25.
Claim 7
Dependent Claim
23 words
The gas sensor of claim 3, wherein said dielectric film is a barium titanate film of permittivity of between about 620 and 1100.
Claim 8
Dependent Claim
48 words
The gas sensor of claims 4, 5 or 6, wherein said contact means includes a metal electrode in contact with the surface of each said diffusion region free of oxide film for providing electrical connection to said diffusion regions and a metal electrode in contact with said gate.
Claim 9
Dependent Claim
11 words
The gas sensor of claim 7 wherein said electrodes are chromium-gold.
Claim 10
Dependent Claim
13 words
The gas sensor of claim 1, wherein said gate material is tin oxide.
Claim 11
Dependent Claim
13 words
The gas sensor of claim 1, wherein said gate material is zinc oxide.
Claim 12
Dependent Claim
13 words
The gas sensor of claim 1, wherein said gate material is ferric oxide.
References Cited (Backward Citations)
US3832700A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1983-12-09 | 1984-06-09 | 1984-12-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-12-09 | 1988-06-09 | 1988-12-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-12-09 | 1992-06-09 | 1992-12-09 | $7700.00 | Window Closed / Lapsed |