| 摘要 |
PROBLEM TO BE SOLVED: To provide a nonvolatile semiconductor memory in which verify is appropriately conducted when multi-valued writing is conducted for nonvolatile memory cell transistors. SOLUTION: Memory cells of a memory array 21 store two bits. A memory array sense amplifier 20 outputs two bits during verify. A writing target value to the memory cells corresponding to each two bits of a page buffer is stored. The value, that defines the process for the memory cells corresponding to each bit of a mask buffer, is stored. A write driver applies writing pulses when the bit in the mask buffer corresponding to a selected memory cell is "0". A verify circuit 54 compares two bits outputted from the memory array sense amplifier 20 with corresponding two bits within the page buffer. When the comparison result is matched and the bit in the corresponding mask buffer is "0", it is rewritten into "1". COPYRIGHT: (C)2006,JPO&NCIPI
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