Static information storage and retrieval – Floating gate – Particular biasing
Reexamination Certificate
2007-03-13
2007-03-13
Nguyen, Viet Q. (Department: 2827)
Static information storage and retrieval
Floating gate
Particular biasing
C365S185300, C365S185330, C365S185240, C365S185180, C365S185220
Reexamination Certificate
active
11141732
ABSTRACT:
The flash memory device according to the present invention includes an erase control circuit, used as a state machine, having embodied erase algorithm which can prevent flash memory cells from being over-erased. The erase control circuit, first, checks whether or not threshold voltages of selected cells reach a predetermined pre-verify voltage higher than the maximum value of a target threshold voltage range corresponding to the erased state. When at least one of the selected cells has its threshold voltage higher than the pre-verify voltage, a high voltage generator generates a bulk voltage that is increased step by step by a predetermined voltage level. And, when the selected cells all have threshold voltages equal to or less than the pre-verify voltage, the high voltage generator generates a constant bulk voltage. According to this bulk voltage control scheme, the number of flash memory cells over-erased at the erase operation is reduced reducing the total erase time.
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Marger & Johnson & McCollom, P.C.
Nguyen Viet Q.
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