Memory device and method of forming the same

A memory device, comprising:

• a first tier of a memory array disposed over a substrate, comprising:
• a stack structure comprising a first dielectric layer, a first conductive layer, a second dielectric layer, a second conductive layer, and a third dielectric layer stacked from bottom to top;
• a first gate pillar structure penetrating through and laterally surrounded by the stack structure;
• a channel layer disposed between the stack structure and the first gate pillar structure;
• and
• a first data storage layer disposed on the first dielectric layer and laterally between the first conductive layer and the channel layer.

A memory device, comprising:

• a stack structure comprising a first conductive layer, a dielectric layer overlying the first conductive layer, and a second conductive layer overlying the dielectric layer;
• an electrode inset into and spaced from the stack structure;
• a semiconductor layer that separates the electrode from the stack structure;
• and
• a data storage layer on a sidewall of the first conductive layer, between the first conductive layer and the semiconductor layer, wherein the data storage layer and the first conductive layer share a common height.