Patent US5045489A successfully refreshed from Google Patents.
US5045489A
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Method of making a high-speed 2-transistor cell for programmable/EEPROM devices with separate read and write transistors
Assignee: Texas Instruments Inc
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Filing: 1989-06-30
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Granted: 1991-09-03
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Expires: 2009-06-30
Abstract
Abstract A 2-transistor cell (26) comprises buried diffused regions (34, 36 and 38) aligned substantially parallel. Floating gates (40) are aligned substantially perpendicular to the diffused regions (34, 36 and 38). A control gate (42) defines a first channel region between first and second diffused regions (34 and 36) to define a read transistor (30) and a second channel region between second and third diffused regions (36 and 38) to define a program transistor. The read transistor (30) and program transistor (32) may be individually optimized according to their respective functions. Further, tunnel windows (70) may be provided for Fowler-Nordheim tunneling.
Inventors
- 👤 Manzur Gill
- 👤 David D. Wilmoth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 04:40
CPC Classifications
H; H10; H10B; H10B41/00; H10B41/30
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
83 words
A method of forming a non-volatile memory comprising the steps of: forming first, second, and third elongate doped regions of a first conductivity type in a substrate of a second conductivity type, said first, second and third doped regions being substantially parallel; forming a floating gate overlying and separated from said first, second and third doped regions; forming a control gate defining a first channel between said first and second doped regions and a second channel between said second and third doped regions.
Claim 2
Independent Claim
83 words
A method of forming a non-volatile memory comprising the steps of: forming first, second, and third elongate doped regions of a first conductivity type in a substrate of a second conductivity type, said first, second and third doped regions being substantially parallel; forming a floating gate overlying and separated from said first, second and third doped regions; forming a control gate defining a first channel between said first and second doped regions and a second channel between said second and third doped regions.
Claim 3
Dependent Claim
37 words
The method of claim 1 wherein said step of forming a control gate comprises the step of forming a control gate having a wide portion over said first channel and a narrow portion over said second channel.
Claim 4
Dependent Claim
29 words
The method of claim 1 and further comprising the step of forming field oxide regions defining the second channel prior to forming said control gate and said floating gate.
Claim 5
Dependent Claim
19 words
The method of claim 1 and further comprising the step of forming trench isolation regions adjacent said second channel.
Claim 6
Dependent Claim
36 words
The method of claim 1 and further comprising the step of doping said first channel with a first ion concentration and doping said second channel with a second ion concentration greater than said first ion concentration.
Claim 7
Dependent Claim
27 words
The method of claim 1 and further comprising the step of forming a gate oxide region overlying said first and second channels and underlying said floating gate.
Claim 8
Dependent Claim
25 words
The method of claim 6 and further comprising the step of forming a tunnel oxide beneath said floating gate to allow programming by Fowler-Nordheim tunnelling.
Claim 9
Dependent Claim
33 words
The method of claim 1 wherein said step of forming said third doped region comprises a step of forming a third doped region having greater width than said first and second doped region.
Claim 10
Dependent Claim
23 words
The method of claim 1 and further comprising the step of forming field oxide regions over said first, second and third doped regions.
Claim 11
Dependent Claim
45 words
The method of claim 1 and further comprising the steps of: forming fourth and fifth elongate doped regions substantially parallel to said first, second and third doped regions; and forming additional floating gates overlying and substantially perpendicular to said third, fourth and fifth doped regions.
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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) | 1994-09-02 | 1995-03-04 | 1995-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-09-02 | 1999-03-04 | 1999-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-09-02 | 2003-03-04 | 2003-09-03 | $7700.00 | Window Closed / Lapsed |