A semiconductor device and a method of manufacturing the semiconductor device are provided. The semiconductor device includes a source structure formed on a base, an etch prevention layer formed on the source structure, bit lines, a stack structure located between the etch prevention layer and the bit lines and including conductive layers and insulating layers that are alternately stacked on each other, and a channel structure passing through the stack structure and the etch prevention layer, wherein a lower portion of the channel structure is located in the source structure and a sidewall of the lower portion of the channel structure is in direct contact with the source structure.