| 摘要 |
PURPOSE: A semiconductor memory device is provided to extend the lifetime of a semiconductor memory device by substituting a multi-value block with two-value block. CONSTITUTION: A plurality of memory cells memorizes the data of n bits on one cell. The n is 2 or more. The data of h bits is memorized in a memory cell(MLC) of a first region(MLB) among the plurality of memory cells. The h is equal to or less than n. The data of i bits is memorized in the memory cell(SLC) of a second region(SLB). The i is less than h. If the number of rewritings of the second region approaches the standard value, the data of i bits are memorized on the memory cell of not the second region but the first region.
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