| 摘要 |
A nonvolatile semiconductor memory device is provided which includes a plurality of memory cells each having a floating gate, wherein a threshold level of each memory cell depends on a value of electric charge in said floating gate of said memory cell, and wherein said threshold level of each memory cell is placed at one of a first area and a second area. A controller is also provided which controls to set each threshold voltage of selected ones of said plurality of memory cells, wherein said controller performs a first setting operation and a verifying operation. The first setting operation shifts threshold voltages of the selected ones of said plurality of memory cells in a direction from said first area to said second area. The verifying operation detects erratic memory cells which have threshold voltages which are on a side of said second area which is opposite of a middle area formed between the first area and the second area.
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