Ferroelectric RAM (FeRAM or FRAM) is a non-volatile random access memory which uses a ferroelectric layer to achieve its functions. A ferroelectric material has the property to have a spontaneous electric polarization. The ferroelectric layer is placed between two conducting electrodes and its polarization state can be reversed by applying an electric field. This is made possible by the presence of independent regions of polarization inside the ferroelectric material, called ferroelectric domains, which evolve with the applied electric field.

 

The switching of the domains toward the electric field explains the existence of a P-E hysteresis loop. The magnitude of polarization at E = 0 V/m is called the remnant polarization Pr, which gives to the memory its non-volatile behavior. So the two binary states correspond to the two polarization states +Pr and –Pr.
FeRAM are known to be quick and to have a low energy consumption. They are already used for RFID, biometric and electronic devices. However, integration methods are complicated and the miniaturization of such devices is difficult, because of the complexity to distinguish the two states of polarization.

So the challenge is to design circuits to integrate ferroelectric layers, and one of the ways is to integrate ferroelectric layers in 3D devices.

Fig.1 : P-E hysteresis loop