Patent ID: 7251158

Claim:
A method of erasing a sector of memory cells to a single data state, the memory cells having three or more data states corresponding to three or more threshold voltage values, the method comprising: performing a block erase operation on the sector of memory cells until all cells of the sector are erased to a threshold voltage generally corresponding to an intermediate value; performing a soft programming operation on an over-erased memory cell of the sector until the threshold voltage of the over-erased memory cell generally corresponds to a final value; programming memory cells of the sector determined to be at or near a threshold voltage corresponding to the final value until the threshold voltage of the memory cells generally correspond to the intermediate value; re-performing the block erase operation on the sector until all cells of the sector are erased to the threshold voltage generally corresponding to the final value; and re-performing a soft programming operation on an over-erased memory cell of the sector until the threshold voltage corresponding to the final value is attained.