A non-volatile memory device includes a plurality of unit cells. Each unit cell includes lower and upper electrodes over a substrate, a conductive organic material layer between the lower and the upper electrodes, and a nanocrystal layer located within the conductive organic material layer, wherein the nanocrystal layer includes a plurality of nanocrystals surrounded by an amorphous barrier. The unit cell receives a plurality of voltage ranges to perform a plurality of operations. A read operation is performed when an input voltage is in a first voltage range. A first write operation is performed when the input voltage is in a second voltage range higher than the first voltage range. A second write operation is performed when the input voltage is in a third voltage range higher than the second voltage range. An erase operation is performed when the input voltage is higher than the third voltage range.