| 摘要 |
After execution of sub-block erase (S 2 ) for partly erasing a memory cell block, sub-block erase verify read is executed (S 4 ). As a result of the sub-block erase verify read, if the sub-block erase is completed, then terminate the sub-block erase (S 5 ). If otherwise the sub-block erase is not completed yet, then perform over-program verify read (S 6 ) to thereby determine whether the cause of an event that a sub-block erase-verify result becomes "Fail" due to the deficiency of erase or the presence of an over-programmed cell or cells. If the result of such over-program verify read is "Pass," then repeat execution of the sub-block erase verify read (S 2 ). When the over-program verify read (S 6 ) is "Fail," output a Fail result and then complete the operation (S 8 ).
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