摘要 |
PROBLEM TO BE SOLVED: To narrow threshold distribution by suppressing write fluctuation in a nonvolatile semiconductor storage device.SOLUTION: When a threshold of a memory cell transistor to be written is less than a first threshold, first writing for applying a first bit line voltage to a bit line is performed. When the threshold of a memory cell transistor to be written is not less than the first threshold and less than a second threshold, second writing for applying a second bit line voltage larger than the first bit line voltage to the bit line is performed. When the threshold of a memory cell transistor to be written is not less than the second threshold and less than a third threshold, third writing for applying a third bit line voltage larger than the second bit line voltage to the bit line is performed. |