| 摘要 |
An erase method having a memory cell array which includes at least one blocks having MLC is disclosed. The erase method includes shifting every threshold voltage distribution into a threshold voltage distribution having highest level by pre-programming every cell in a block selected for erase, performing an erase operation on the pre-programmed memory block, performing a soft program and a verifying operation on the memory block, dividing the memory block into a first group and a second group in case that the memory block is passed, performing a verifying operation on the first group, and performing a soft program and a verifying operation on the first group in case that the first group is not passed, and performing a verifying operation on the second group in case that the first group is passed, and performing a soft program and a verifying operation on the second group in case that the second group is not passed.
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