Non-volatile semiconductor memory device for selectively re-checking word lines

A non-volatile semiconductor memory device, comprising:

• a plurality of memory cells;
• and
• a plurality of word lines, each being coupled to a plurality of said memory cells;
• wherein an erasing process is executed to change the threshold voltage of a memory cell from a first threshold voltage to a second threshold voltage,
• wherein a rewriting process is executed to an over erased memory cell, and
• wherein during said rewriting process a pulse voltage increased step by step is inflicted to said memory cell .

A non-volatile semiconductor memory device, comprising:

• a plurality of word lines, each of which being coupled to a plurality of memory cells;
• a selector for selecting a group of word lines among said plurality of word lines via which data therein is to be erased;
• erasing means for inflicting a predetermined voltage by increments onto each memory cell of each of selected word lines so as to erase the data therein by changing a threshold voltage of said each memory cell;
• checking means for checking whether the data in said each memory cell is erased completely so as to decide whether to inflict next voltage increment on said each memory cell and for checking whether all memory cells in each of selected word lines is erased completely;
• and
• a latch circuit for blocking unselected word lines and completely erased memory cells from being checked.