SELF-SELECTING MEMORY DEVICE HAVING POLARITY DEPENDENT THRESHOLD VOLTAGE SHIFT CHARACTERISTICS AND MEMORY APPARATUS INCLUDING THE SAME

Provided are a self-selecting memory device having polarity dependent threshold voltage shift characteristics and/or a memory apparatus including the self-selecting memory device. The memory device includes a first electrode, a second electrode apart from and facing the first electrode, and a memory layer between the first electrode and the second electrode. The memory layer has Ovonic threshold switching characteristics and is configured to have a threshold voltage of the memory layer be changed as a density of active traps in the memory layer is changed, the threshold voltage changing according to the polarity and the intensity of a bias voltage applied to the memory layer. Furthermore, an element composition distribution is configured to be maintained constant in the memory layer in response to the threshold voltage of the memory layer changing.