Kabushiki Kaisha Toshiba

Ryu Hondai

Yasuhiko Honda

Takahiro Suzuki

Takamichi Kasai

Shinya Fujisawa

Yuji Komine

Manabu Satoh

A method for controlling a threshold value in a nonvolatile semiconductor memory device, includes: performing writing at least once on at least one of the memory cells to be adjusted to a state other than an erased state with an applied voltage that does not cause excess writing, with verify reading being not performed; and performing verify reading by applying a verify voltage corresponding to a target threshold value of the memory cell after the writing is performed on the at least one of the memory cells to be adjusted to the state other than the erased state, and, when the threshold value of the memory cell is determined to be lower than the target threshold value, repeating the writing with the applied voltage that does not cause excess writing and the verify reading until the threshold value of the memory cell becomes equal to or higher than the target threshold value.

Method for controlling threshold value in nonvolatile semiconductor memory device

A non-volatile semiconductor storage device includes a memory cell array having a plurality of non-volatile memory cells, an address search circuit which searches for write object data and outputs an address where the write object data is present, when writing data into the non-volatile memory cells, and a control circuit which exercises control to write the write object data into the non-volatile memory cells in accordance with the address output from the address search circuit.

Non-volatile semiconductor storage device with address search circuit used when writing

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Ryu Hondai