Three-dimensional memory devices having a plurality of nand strings

A three-dimensional (3D) memory device, comprising:

• a substrate;
• a memory string extending vertically on and above the substrate;
• a peripheral device above the memory string;
• a semiconductor layer above the peripheral device, wherein the peripheral device is at a first surface of the semiconductor layer;
• and
• a first interconnect layer on a second surface of the semiconductor layer.

A three-dimensional (3D) memory device, comprising:

• a substrate;
• an alternating conductor/dielectric stack on and above the substrate;
• a peripheral device above the alternating conductor/dielectric stack;
• and
• a plurality of memory strings extending vertically through the alternating conductor/dielectric stack, wherein each of the plurality of memory strings comprises:
• a semiconductor channel extending vertically through the alternating conductor/dielectric stack;
• a tunneling layer between the alternating conductor/dielectric stack and the semiconductor channel;
• a storage layer between the tunneling layer and the alternating conductor/dielectric stack;
• and
• an epitaxial plug at a lower end of the memory string and in contact with the substrate.