Patent US3877055A successfully refreshed from Google Patents.
US3877055A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Semiconductor memory device
Assignee: Motorola Solutions Inc
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Filing: 1974-04-12
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Granted: 1975-04-08
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Expires: 1994-04-12
Abstract
Abstract A fixed threshold MNOS device and a variable threshold MNOS device internally connected in series with a diffused area in the substrate, having a conductivity type opposite that of the substrate, in contact with both of the devices to provide a common source-drain. The diffused area forming the common sourcedrain is added to remove variations in channel length in the devices.
Inventors
- 👤 John Andrew Fisher
- 👤 Michael William Powell
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 09:37
CPC Classifications
G; G11; G11C; G11C16/00; G11C16/02; G11C16/04; G11C16/0466; H; H10; H10D; H10D30/00; H10D30/60; H10D30/69; H10D84/00; H10D84/80; H10D84/82; H10D84/83
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
207 words
AN IMPROVED SEMICONDUCTOR MEMORY DEVICE COMPRISING: A. A SUBSTRATE HAVING A FIRST TYPE OF CONDUCTIVITY; B. AT LEAST FIRST, SECOND AND THIRD DIFFUSION AREAS LOCATED IN SPACED APART RELATIONSHIP IN SAID SUBSTRATE AND HAVING A CONDUCTIVITY TYPE OPPOSITE THAT OF SAID SUBSTRATE; C. ALTERABLE THRESHOLD GATE MEANS INCLUDING A FIRST RELATIVELY THIN LAYER OF METAL OXIDE DISPOSED IN CONTACT WITH SAID FIRST AND SECOND DIFFUSION AREAS AND SAID SUBSTRATE THEREBETWEEN AND A SECOND LAYER OF METAL NITRIDE DISPOSED OVER SAID THIN LAYER OF METAL OXIDE; D. FIXED THRESHOLD GATE MEANS INCLUDING A FIRST RELATIVELY THICK LAYER OF METL OXIDE DISPOSED IN CONTACT WITH SAID SECOND AND THIRD DIFFUSION AREAS AND SAID SUBSTRATE THEREBETWEEN AND A SECOND LAYER OF METAL NITRIDE DISPOSED OVER SAID THICK LAYER OF METAL OXIDE, SAID THIN LAYER OF METAL OXIDE AND SAID RELATIVELY THICK LAYER OF METAL OXIDE BEING CONTIGUOUS TO EACH OTHER AT AN INTERFACE, SAID SECOND DIFFUSION REGION BEING DISPOSED IN SAID SUBSTRATE AND AT LEAST A PORTION THEREOF BEING LOCATED UNDER SAID INTERFACE; E. FIRST AND SECOND OHMIC CONTACT MEANS DISPOSED IN CONTACT WITH SAID FIRST AND SAID THIRD DIFFUSION AREAS, RESPECTIVELY; AND F. A SINGLE GATE ELECTRODE MEANS DISPOSED IN CONTACT WITH BOTH SAID ALTERABLE AND FIXED THRESHOLD GATES.
Claim 2
Dependent Claim
207 words
AN IMPROVED SEMICONDUCTOR MEMORY DEVICE COMPRISING: A. A SUBSTRATE HAVING A FIRST TYPE OF CONDUCTIVITY; B. AT LEAST FIRST, SECOND AND THIRD DIFFUSION AREAS LOCATED IN SPACED APART RELATIONSHIP IN SAID SUBSTRATE AND HAVING A CONDUCTIVITY TYPE OPPOSITE THAT OF SAID SUBSTRATE; C. ALTERABLE THRESHOLD GATE MEANS INCLUDING A FIRST RELATIVELY THIN LAYER OF METAL OXIDE DISPOSED IN CONTACT WITH SAID FIRST AND SECOND DIFFUSION AREAS AND SAID SUBSTRATE THEREBETWEEN AND A SECOND LAYER OF METAL NITRIDE DISPOSED OVER SAID THIN LAYER OF METAL OXIDE; D. FIXED THRESHOLD GATE MEANS INCLUDING A FIRST RELATIVELY THICK LAYER OF METL OXIDE DISPOSED IN CONTACT WITH SAID SECOND AND THIRD DIFFUSION AREAS AND SAID SUBSTRATE THEREBETWEEN AND A SECOND LAYER OF METAL NITRIDE DISPOSED OVER SAID THICK LAYER OF METAL OXIDE, SAID THIN LAYER OF METAL OXIDE AND SAID RELATIVELY THICK LAYER OF METAL OXIDE BEING CONTIGUOUS TO EACH OTHER AT AN INTERFACE, SAID SECOND DIFFUSION REGION BEING DISPOSED IN SAID SUBSTRATE AND AT LEAST A PORTION THEREOF BEING LOCATED UNDER SAID INTERFACE; E. FIRST AND SECOND OHMIC CONTACT MEANS DISPOSED IN CONTACT WITH SAID FIRST AND SAID THIRD DIFFUSION AREAS, RESPECTIVELY; AND F. A SINGLE GATE ELECTRODE MEANS DISPOSED IN CONTACT WITH BOTH SAID ALTERABLE AND FIXED THRESHOLD GATES.
Claim 3
Dependent Claim
17 words
An improved semiconductor memory device as claimed in claim 1 wherein said metal oxide includes silicon dioxide.
Claim 4
Dependent Claim
17 words
An improved semiconductor memory device as claimed in claim 1 wherein said metal nitride includes silicon nitride.
Claim 5
Dependent Claim
30 words
An improved semiconductor memory device as claimed in claim 1 wherein said substrate has an N-type conductivity and the first, second and third diffusion areas each have a P-type conductivity.
Claim 6
Dependent Claim
24 words
An improved semiconductor memory device as claimed in claim 1 wherein the relatively thin layer of metal oxide is less than 50 angstroms thick.
Claim 7
Dependent Claim
28 words
An improved semiconductor memory device as claimed in claim 1 wherein the relatively thin layer of metal oxide is in the range of 20 to 30 angstroms thick.
Claim 8
Dependent Claim
29 words
An improved semiconductior memory device as claimed in claim 1 wherein the relatively thick layer of metal oxide is in the range of approximately 300 to 500 angstroms thick.
References Cited (Backward Citations)
US3436622A
Cited
US3719866A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-04-07 | 1978-10-07 | 1979-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-04-07 | 1982-10-07 | 1983-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-04-07 | 1986-10-07 | 1987-04-08 | $7700.00 | Window Closed / Lapsed |