Semiconductor structure and method of forming the same

A semiconductor structure includes a substrate, a first electrode, a vacancy supply layer, a sidewall barrier layer, an oxygen reservoir layer, a resistive switching layer, and a second electrode. The first electrode is disposed on the substrate. The vacancy supply layer is disposed on the first electrode. The sidewall barrier layer is disposed on the first electrode. The oxygen reservoir layer is disposed on the first electrode. The sidewall barrier layer is disposed between the oxygen reservoir layer and the vacancy supply layer. The resistive switching layer is disposed on the vacancy supply layer. The second electrode is disposed on the resistive switching layer.