| 摘要 |
A NAND flash memory device and a program method thereof are provided to prevent program prohibition before a memory cell reaches '01' state when an MSB(Most Significant Bit) program is performed from '11' state to '01' state, by performing a multi-bit program operation. According to a multi-bit program method of a NAND flash memory device, LSB(Least Significant Bit) data is programmed in a memory cell. The LSB data read out from the memory cell is stored in a cache register. MSB data stored in a main register is programmed in the memory cell. Data read out from the memory cell is stored in the main register during a first verify operation(S740). Data read out from the memory cell is stored in the cache register during a second verify operation(S750). The data in the cache register is transferred to the main register(S760).
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