A semiconductor memory includes bit lines, memory cells and a sense
amplifier both of which are connected to the bit lines. Each of the memory
cells includes a transistor and a capacitor. The capacitor is made of a
material having a quantity of residual dielectric polarization in an
electroless state in a hysteresis characteristic that is not reduced to
less than a threshold value until after a lapse of a time of a refreshing
cycle. The refresh cycle includes clock cycles. The sense amplifier
detects an output current on the bit lines due to the residual dielectric
polarization. The sense amplifier amplifies the output current to refresh
the quantity of residual dielectric polarization of the capacitor when the
detected level is equal to or larger than the threshold value. The sense
amplifier does not amplify the output current when the detected level is
less than the threshold value.
