Resistive switching memory device including dual active layer and array including the same

A resistive switching memory device comprising:

• a lower electrode;
• an amorphous metal oxide-based first active layer positioned on the lower electrode;
• an amorphous metal oxide-based second active layer positioned on the first active layer;
• and
• an upper electrode positioned on the second active layer,
• wherein the first active layer and the second active layer are made of the same substance but are different in electrical characteristic and
• wherein the resistive switching memory device has:
• (a) a first resistance state in which a first positive voltage is applied between the upper electrode and the lower electrode so the first active layer is set into a low-resistance state;
• (b) a second resistance state in which a second positive voltage is applied between the upper electrode and the lower electrode so the first active layer and the second active layer are set into a low-resistance state;
• and
• (c) a third resistance state in which a third positive voltage is applied between the upper electrode and the lower electrode so the first active layer and the second active layer are reset into a high-resistance state.