U.S. patents available from 1976 to present.
U.S. patent applications available from 2005 to present.

Two square NVRAM cell

Patent 6040218 Issued on March 21, 2000. Estimated Expiration Date: Icon_subject September 13, 2019. Estimated Expiration Date is calculated based on simple USPTO term provisions. It does not account for terminal disclaimers, term adjustments, failure to pay maintenance fees, or other factors which might affect the term of a patent.

Patent References

Shadow ram cell having a shallow trench eeprom
Patent #: 5196722
Issued on: 03/23/1993
Inventor: Bergendahl, et al.

Method of making shadow RAM cell having a shallow trench EEPROM
Patent #: 5399516
Issued on: 03/21/1995
Inventor: Bergendahl, et al.

Three-dimensional direct-write EEPROM arrays and fabrication methods
Patent #: 5467305
Issued on: 11/14/1995
Inventor: Bertin, et al.

Non-volatile random access memory cell constructed of silicon carbide
Patent #: 5510630
Issued on: 04/23/1996
Inventor: Agarwal, et al.

Process for forming a polysilicon electrode in a trench
Patent #: 5656544
Issued on: 08/12/1997
Inventor: Bergendahl, et al.

Low voltage EEPROM/NVRAM transistors and making method
Patent #: 5780341
Issued on: 07/14/1998
Inventor: Ogura

Method of making trench EPROM simultaneously with forming a DRAM cell Patent #: 5930619
Issued on: 07/27/1999
Inventor: Noble

Inventor

Application

No. 394093 filed on 09/13/1999

US Classes:

438/259, Including forming gate electrode in trench or recess in substrate257/E21.693, For vertical channel (EPO)257/E27.103, Electrically programmable ROM (EPO)438/270, Gate electrode in trench or recess in semiconductor substrate438/589Recessed into semiconductor substrate

Examiners

Primary: Phan, Trong

Attorney, Agent or Firm

International Class

H01L 021/824.7

Abstract

A non-volatile random access memory (NVRAM) cell and method of fabrication thereof. Pairs of NVRAM cells, each including three FETs stacked in a NAND-like structure are formed vertically in silicon pillars. Source devices at the bottom of the pillar selectively provide ground to one of the cells. A floating gate extends upward from the source device's gate line. A control gate plate extending between adjacent pillars selectively provides a programming voltage to the control gate. Both the source gate and the control gate are capacitively coupled through silicon rich oxide to the floating gate. Polysilicon plugs between silicon pillars are word line gates for cells in adjacent pillars. A diffusion at the top of each pillar is a bit line contact for both cells at the pillar. Each pair of cells on a pillar are on a common bit line and a common word line. The word line, control gate and source gate line select individual cells in the pair.

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