Semiconductive metal oxide ferroelectric memory transistor: A long-retention nonvolatile memory transistor

The retention problem is a technical challenge for one-transistor (1T) ferroelectric memory devices. Three possible mechanisms are responsible for the poor retention of one-transistor ferroelectric memories: namely, charges trapping within the gate oxide and ferroelectric film, floating gate effect, and the depolarization field. In order to overcome these problems, a novel ferroelectric transistor design using a semiconductive oxide film in place of the gate dielectric has been fabricated. There is no insulator, other than the ferroelectric thin film in the gate stack; therefore, there is a very low depolarization field. The bottom gate of the ferroelectric capacitor is electrically connected to the silicon substrate through the semiconductive metal oxide resulting in the improvement of the memory retention characteristics.