Memory device

A memory device, comprising:

• a substrate;
• a memory unit disposed on the substrate, wherein the memory unit comprises:
• a first electrode;
• a second electrode disposed above the first electrode in a vertical direction;
• and
• a memory material layer disposed between the first electrode and the second electrode in the vertical direction;
• a first spacer layer disposed on a sidewall of the memory unit, wherein the first spacer layer comprises:
• a first portion disposed on a sidewall of the first electrode;
• a second portion disposed on a sidewall of the second electrode, wherein a thickness of the second portion in a horizontal direction is greater than a thickness of the first portion in the horizontal direction;
• and
• a bottom portion;
• and
• a second spacer layer disposed on the first spacer layer, wherein a material composition of the second spacer layer is different from a material composition of the first spacer layer, and the bottom portion of the first spacer layer is disposed between the substrate and the second spacer layer in the vertical direction.