1. A nonvolatile memory device, comprising: at least one switching device; and at least one storage node electrically connected to the at least one switching device; wherein the at least one storage node includes a lower electrode, one or more oxygen-deficient metal oxide layers, one or more data storage layers, and an upper electrode, at least one of the one or more metal oxide layers is electrically connected to the lower electrode, at least one of the one or more data storage layers is electrically connected to at least one of the one or more metal oxide layers, the upper electrode is electrically connected to at least one of the one or more data storage layers, the storage node is configured to absorb oxygen at one or more oxygen vacancies of the one or more metal oxide layers upon application of a voltage, at least one of the one or more metal oxide layers includes one or more of ITO, IZO, RuO 2 , ZnO, and ZrO, at least one of the one or more data storage layers includes one or more of Al 2 O 3 , CoO, Nb 2 O 5 , NiO, TiO 2 , V 2 O 5 , WO 3 , and ZnO, and a material of at least one of the metal oxide layers is different from a material of at least one of the data storage layers.