Nonvolatile data storage, semicoductor memory device including nonvolatile data storage and method of forming the same

A data storage of a semiconductor device, the data storage comprising:

• a lower electrode;
• a first discharge prevention layer stacked on the lower electrode;
• a phase-transition layer on the first discharge prevention layer, the phase-transition layer including oxygen and exhibiting two different resistance characteristics depending on whether an insulating property thereof has been changed;
• a second discharge prevention layer stacked on the phase-transition layer;
• and
• an upper electrode stacked on the second discharge layer,
• wherein the first and second discharge prevention layers are metal oxide layers including a tantalum oxide layer or an aluminum oxide layer adapted to block discharge of the oxygen from the phase-transition layer.