There are provided a semiconductor memory device and a manufacturing method of the semiconductor memory device. The semiconductor memory device includes: a channel structure including a first pillar part and a second pillar part extending from the first pillar part; a blocking insulating layer surrounding a sidewall of the first pillar part; a data storage layer disposed between the first pillar part and the blocking insulating layer; an upper select line overlapping with an end portion of the blocking insulating layer and an end portion of the data storage layer, which face in an extending direction of the second pillar part, the upper select line surrounding a sidewall of the second pillar part; and a tunnel insulating layer disposed between the first pillar part and the data storage layer, the tunnel insulating layer extending between the second pillar part and the upper select line.