Memory device and method of forming the same

A method of forming a memory device, comprising:

• forming a first conductive line above a memory region of a substrate and a second conductive line above a peripheral region of the substrate;
• forming a capacitor above the first conductive line;
• forming a bottom portion of a contact structure above the second conductive line;
• forming a first dielectric layer covering the capacitor and the bottom portion of the contact structure;
• forming a first opening and a second opening in the first dielectric layer, wherein the first opening is above the capacitor, and the second opening exposes the bottom portion of the contact structure;
• filling a conductive material in the first opening and the second opening such that a middle portion of the contact structure is formed in the second opening and a gate material is formed in the first opening;
• forming a third opening in the gate material to form a gate structure in the first opening;
• forming a gate dielectric layer and a channel in the third opening;
• and
• forming a bit line to be connected to the channel and the contact structure.