Patent US5955746A successfully refreshed from Google Patents.
US5955746A
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SRAM having enhanced cell ratio
Assignee: MagnaChip Semiconductor Ltd
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Filing: 1997-03-27
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Granted: 1999-09-21
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Expires: 2017-03-27
Abstract
Abstract An SRAM cell and a method of manufacturing the same are disclosed. An SRAM cell including pull down devices, access devices and pull up devices each having source and drain regions with LDD structure, the source and drain regions of the access devices having: N + source and drain regions; N - source and drain regions formed under the N + source and drain regions; and P - impurity regions whose predetermined portion is overlapped with the N - source and drain region.
Inventors
- 👤 Jae-Kap Kim
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 18:20
CPC Classifications
H; H10; H10B; H10B10/00; H10B10/12; H10D; H10D84/00; H10D84/01; H10D84/0123; H10D84/0126; H10D84/0165; H10D84/017; H10D84/80; H10D84/82; H10D84/83; H10D84/85; Y; Y10; Y10S; Y10S257/00; Y10S257/903; Y10S257/904
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
59 words
An SRAM cell including pull down devices, access devices and pull up devices, wherein source and drain regions of said access device comprise: N+ source and drain regions; N- source and drain regions formed under said N+ source and drain regions; and a P- impurity region wherein predetermined portion thereof is overlapped with said N- source and drain regions.
Claim 2
Dependent Claim
59 words
An SRAM cell including pull down devices, access devices and pull up devices, wherein source and drain regions of said access device comprise: N+ source and drain regions; N- source and drain regions formed under said N+ source and drain regions; and a P- impurity region wherein predetermined portion thereof is overlapped with said N- source and drain regions.
Claim 3
Dependent Claim
48 words
The SRAM cell as claimed in claim 1, wherein a concentration of N type impurity of a region in which said P- impurity region and said N- source and drain regions of said access devices are overlapped is lower than that of said N- source and drain regions.
Claim 4
Dependent Claim
52 words
The SRAM cell as claimed in claim 2, wherein said concentration of N type impurity region of the overlapped portion of said access devices is 1×10 18 to 2×10 18 ions/cm 3 , and that of the N - source and drain regions is 2×10 18 to 5×10 18 ions/cm 3 .
Claim 5
Dependent Claim
18 words
The SRAM cell as claimed in claim 1, wherein said pull up devices are P channel bulk MOSFETs.
Claim 6
Dependent Claim
15 words
The SRAM cell as claimed in claim 1, wherein said pull up device are resistors.
Claim 7
Dependent Claim
18 words
The SRAM cell as claimed in claim 1, wherein said pull up device are P channel polysilicon TFTs.
References Cited (Backward Citations)
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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) | 2002-09-20 | 2003-03-22 | 2003-09-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2006-09-20 | 2007-03-22 | 2007-09-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2010-09-20 | 2011-03-22 | 2011-09-21 | $7700.00 | Window Closed / Lapsed |