Non-volatile memory elements and memory devices including the same

A memory device comprising:

• a plurality of first wirings arranged in parallel with one another;
• a plurality of second wirings crossing the first wirings and arranged in parallel with one another;
• and
• a first memory cell formed at each cross-point between the plurality of first wirings and the plurality of second wirings, each first memory cell including,
• a memory layer disposed between the first wiring and the second wiring, and including a first material layer and a second material layer configured to exchange ionic species to change a resistance state of the memory layer, and
• a buffer layer disposed between the memory layer and the first wiring;
• wherein
• the first material layer is an oxygen supplying layer and the second material layer is an oxygen exchanging layer,
• an oxygen concentration of the oxygen exchanging layer increases one of gradually and in stages in a direction from the oxygen supplying layer to the second wiring,
• the oxygen exchanging layer includes a first region having a first oxygen concentration and a second region having a second oxygen concentration, the second oxygen concentration being greater than the first oxygen concentration,
• the first region is in direct contact with the oxygen supplying layer, and
• the second region is in direct contact with an intermediate electrode disposed between the first wiring and the second wiring.