Non-volatile semiconductor memory device

Details Non-volatile semiconductor memory device Non-volatile semiconductor memory device

1995-04-25

1996-11-19

Nguyen, Tan T.

Static information storage and retrieval

Floating gate

Particular biasing

365218, G11C 700

Patent

active

055769942

ABSTRACT:
When an erase voltage is applied to the sources of data erasable and rewritable memory cells each having a floating gate, the erasure characteristics of the memory cells can be improved by controlling the rise time of the erase voltage or by increasing the erase voltage stepwise. In test mode, no row lines are selected by a row decoder and further the sources of the respective memory cells are set to ground level. Under these conditions, in case there exists an overerased memory cell, this cell is turned on due to depletion, so that it is possible to detect the presence of the overerased memory cell on the basis of change in potential of the column line connected to this turned on memory cell. A differential amplifier is used to detect the change in potential of the column line. In the test mode, the potential of the column lines is compared with a reference potential applied to a dummy column line, and a source bias generating circuit applies a test potential suitable for test to the respective sources of the cells, to shift the threshold level of the respective cells in a positive direction, for instance. By applying this test potential to the cells, it is possible to detect the pseudo-threshold level shifted in the positive direction; that is, to detect the overerased status of the memory cell more properly. Further, the erasure is effected until the threshold level of a memory cell of the highest erasure speed reaches a predetermined level, irrespective of the threshold distribution width of the memory cells, thus realizing a higher speed access to the device of narrower threshold distribution width, as compared with the conventional device.

REFERENCES:
patent: 4641284 (1987-02-01), Suzuki
patent: 4841482 (1989-06-01), Kreifels et al.
patent: 4860261 (1989-08-01), Kreifels et al.
patent: 4905194 (1990-02-01), Ohtsuka et al.
patent: 4982364 (1991-01-01), Iwahashi
patent: 5142496 (1992-08-01), Van Buskirk
patent: 5157626 (1992-10-01), Watanabe
patent: 5197028 (1993-03-01), Nakai
patent: 5214604 (1993-05-01), Kato
patent: 5241507 (1993-08-01), Fong
patent: 5297079 (1994-03-01), Ha
patent: 5315547 (1994-05-01), Shoji et al.

Affiliated with

Also associated with

Rating

Non-volatile semiconductor memory device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Non-volatile semiconductor memory device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Non-volatile semiconductor memory device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-546175