Memory devices and methods of operating the same. A memory cell of a memory device may include a ferroelectric layer and a semiconductor layer bonded to each other. The ferroelectric layer may be of a p-type and the semiconductor layer may be of an n-type. The memory cell may have a switching characteristic due to a depletion region that exists in a junction between the ferroelectric layer and the semiconductor layer. The memory device may be a device writing data using a polarization change of the ferroelectric layer.