| 摘要 |
In a ferro-electric memory including reference cells, if one reference cell is associated with a plurality of normal cells, a period in which "L" data is written in the reference cell and a period in which "H" data is written or read out in/from the reference cell are controlled to be shorter than a period in which "L" data is written in each normal cell and a period in which "H" data is written or read out in/from each normal cell, respectively. In this manner, stress applied to the reference cell is reduced and, even if writing or reading is repeatedly performed on the normal cells, the reliability of the reference cell is enhanced and deterioration in characteristics of the reference cell due to repetitive rewriting of data is suppressed.
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