| 摘要 |
A method in performing an erasure operation of a nonvolatile memory device includes a step of performing a block erasure operation wherein a plurality of memory cells in a selected block are erased at once, a step of selecting an over-programmed memory cell having a threshold voltage higher than an upper bound verification voltage, and a step of erasing selectively the over-programmed memory cell. A nonvolatile memory device comprises a cell array comprising a plurality of memory cells wherein the memory cells have a desired threshold voltage distribution for a state of being erased, wherein the distribution spreads over between a lower bound verification voltage and an upper bound verification voltage, a voltage generator configured to provide a word line voltage and a bit line voltage to word lines and bit lines of the plurality of memory cells respectively, a write driver and sense amplifier configured to write data or read out data through bit lines of the plurality of memory cells, and a control logic configured to control the voltage generator and the write driver and sense amplifier to perform a post-erasure operation of selecting and erasing an over-programmed memory cell having a threshold voltage higher than the upper bound verification voltage. |
