Semiconductor memory device and method of manufacturing the same

A method of manufacturing a semiconductor memory device, the method comprising:

• forming a stack in which a plurality of first material layers and a plurality of second material layers are alternately disposed on a base;
• forming a channel hole that passes through the stack and sequentially forming a memory layer, a channel layer, a backgate insulating layer, and a backgate on a sidewall of the channel hole, thereby forming a vertical channel structure;
• performing an etching process such that an upper surface of the backgate is arranged at a position lower than that of an uppermost second material layer among the plurality of second material layers, and forming a first gap insulating layer in a region where the backgate is etched;
• forming a line-shaped trench that exposes the upper surface of the backgate and overlaps the vertical channel structure and the stack, thereby separating an upper end of the vertical channel structure into a first portion and a second portion, each having a semicircular structure;
• forming a second gap insulating layer that contacts a surface of the channel layer that is exposed by the trench;
• forming, on a lower surface of the trench, a third material layer that contacts the upper surface of the backgate and the uppermost second material layer;
• forming a slit that passes through the stack and then removing the plurality of second material layers and the third material layer that are exposed through the slit;
• and
• filling a recessed area from which the plurality of second material layers and the third material layer are removed with a conductive material, thereby forming a conductive layer corresponding to a backgate line and a plurality of conductive layers corresponding to word lines.