Static information storage and retrieval – Floating gate – Particular connection
Patent
1997-05-15
1998-09-22
Nelms, David C.
Static information storage and retrieval
Floating gate
Particular connection
36518522, G11C 1604
Patent
active
058124519
ABSTRACT:
A semiconductor storage apparatus and a method of writing data to the semiconductor storage apparatus can restrict the threshold value of the memory cells, to which data has been written or from which data has been erased, to be included in a predetermined range without excessive writing by performing a verifying operation. In the writing operation, writing is performed such that a first determining level is set to a loose level which is the same as the level set for the reading operation or higher than the loose level but lower than a finally required determining level. In accordance with the first determining level, a first writing operation is performed. Then, a second writing operation is performed in accordance with a second determining level. The threshold value of a memory cell having a threshold value between the first determining level, which is the loose level, and the second determining level which is the required determining level (an aimed determining level) is raised to be higher than the second determining level, that is, the writing operation is performed by two steps. When the width of the distribution of the threshold values is reduced, data can reliably be erased from all of the memory cells when data is collectively erased in the erasing operation.
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Kabushiki Kaisha Toshiba
Nelms David C.
Nguyen Hien
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