Patent attributes
A nonvolatile decision memory unit stores decision data indicating whether data stored in the normal memory cells is true or false. An inversion control circuit sets the inverting signal to a valid level with a predetermined probability. A write circuit writes data having logic which is inverse logic of data to be rewritten to the normal memory cells and writes decision data indicating false to the decision memory unit when the inverting signal indicates a valid level. Since inverse data is rewritten at a predetermined frequency, an imprint is prevented when a read operation is executed repetitively. Moreover, since frequent repeating of reverse polarization of the ferroelectric capacitor due to a rewrite operation is prevented, deterioration of the ferroelectric capacitor due to reverse polarization is minimized. Thus, occurrence of the imprint and deterioration of characteristics in the ferroelectric capacitor is prevented, and the reliability of the ferroelectric memory is improved.
