| CPC H10B 63/20 (2023.02) [H10B 61/10 (2023.02)] | 8 Claims |

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1. A selection device, comprising:
a first electrode;
a second electrode disposed to face the first electrode;
a selector layer comprising at least three first selector layers and at least two second selector layers disposed between the first electrode and the second electrode and comprising a metal concentration profile; and
a diffusion barrier to prevent diffusion of a metal doped in the selector layer,
wherein the metal concentration profile comprises a metal concentration of a metal doped in the at least three first selector layers higher than a metal concentration of a metal doped in the at least two second selector layer,
wherein the diffusion barrier layer is disposed between the second electrode and the one of the at least three first selector layers, and is disposed between the one of the at least three first selector layers and the one of the at least two second selector layers, to separate the one of the at least three first selector layers from the one of the at least two second selector layers, and controls changes in the metal concentration profile that may occur during diffusion of the metal and maintains the metal concentration profile constant,
wherein the metal concentration for one of the at least three first selector layer adjacent to the first electrode is different from the one of the at least three first selector layer disposed between the first electrode and the second electrode, and
wherein the metal concentration for one of the at least two second selector layer adjacent to the first electrode is different from the one of the at least two second selector layer adjacent to the second electrode.
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