| 摘要 |
Memory cell currents flowing through memory cells in reading data are compared with reference currents that are set in accordance with the wiring widths of word lines connected to these memory cells. The logic levels of data retained in the memory cells are detected depending on whether larger or smaller the memory cell currents are than the reference currents. Setting a plurality of reference currents for every wiring width of word lines allows the reference currents to be set at optimum values for each memory cell having different gate widths. Since the reference currents are set according to the characteristic of memory cells, read margins improve for enhanced reliability in read operations.
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