Three-dimensional nand memory device and method of forming the same

A method for manufacturing a semiconductor device, comprising:

• forming a base layer over an array substrate, the base layer having a first side and an opposing second side that is in contact with the array substrate;
• forming an memory cell structure over the first side of the base layer, the memory cell structure including a stack of alternating word line layers and insulating layers positioned over the first side of the base layer, and a channel structure extending through a first region of the stack in a vertical direction and further extending into the base layer from the first side;
• removing the array substrate so that the second side of the base layer is uncovered;
• and
• forming a plurality of connection structures over the second side of the base layer, the connection structures including a first connection structure that is coupled to the channel structure.

A semiconductor device, comprising:

• a transistor formed in a first side of a substrate;
• an memory cell structure formed over a first side of a base layer;
• and
• a plurality of connection structures formed over an opposing second side of the base layer, wherein the memory cell structure includes:
• a stack of alternating word line layers and insulating layers positioned over the first side of the base layer, the stack including a first region and a second region,
• a channel structure extending through the first region of the stack in a vertical direction and further extending into the base layer from the first side, and
• a plurality of word line contacts extending from respective word line layers in the second region of the stack, the second region of the stack having a stair-cased configuration,
• wherein:
• the connection structures include a first connection structure that is coupled to the channel structure, and
• the first side of the substrate and the first side of the base layer are aligned facing each other so that the transistor and the channel structure are coupled to each other.