Resistance changing device and method for fabricating the same
A resistance changing device includes a resistive layer of a hetero structure interposed between a lower electrode and an upper electrode, and including a plurality of resistive material layers, each having a different resistivity, stacked therein, wherein resistivities of the resistive material layers decrease from the lower electrode toward the upper electrode. Since the resistive layer has a hetero structure in which a plurality of resistive material layers, each having a different resistivity, are stacked in such a manner that the resistivity decreases as it goes from the lower electrode to the upper electrode, it is possible to improve the distributions of the set/reset voltage and the set/reset current, while reducing a reset current of a resistance changing device at the same time.
1. A resistance changing device, comprising:
a resistive layer of a hetero structure including a first resistive material layer and a second resistive material layer, wherein the first resistive material layer is disposed over a lower electrode, the second resistive material layer is disposed over the first resistive material layer, and the second resistive material layer has a lower resistivity than the first resistive material layer; and
an upper electrode disposed over the resistive layer,
wherein the first resistive material layer includes a plurality of conductive filaments penetrating the first resistive material layer to connect the lower electrode to the second resistive material layer,
wherein the second resistive material layer is thinner than the first resistive material layer.
2. The resistance changing device of claim 1 , wherein the first and second resistive material layers include a plurality of vacancies and the conductive filaments are generated from the vacancies in the first resistive material layer.
3. The resistance changing device of claim 1 , wherein the first and second resistive material layers include a metal oxide.
4. The resistance changing device of claim 3 , wherein the first resistive material layer includes a titanium oxide and the second resistive material layer includes a nickel oxide.
5. The resistance changing device of claim 1 , wherein the first and second resistive material layers include a metal oxide doped with a reduced metal.
6. The resistance changing device of claim 5 , wherein the reduced metal has a greater reactivity with oxygen than a metal constituting the metal oxide.
7. The resistance changing device of claim 6 , wherein the first resistive material layer includes a titanium oxide doped with gadolinium and the second resistive material layer includes a nickel oxide doped with titanium.