US Patent 7133306 Semiconductor memory device for securely retaining data

To a bit line to which a memory cell having a ferroelectric capacitor is connected, a guarantee cell having a ferroelectric capacitor is connected. During a read operation of data from the memory cell, data is read out from the memory cell, and the data read out from the memory cell by destructive reading is written automatically to the guarantee cell, so that the data is retained securely as nonvolatile binary data regardless of operating condition, and thus loss of data can be suppressed.