METHOD OF MANUFACTURING SEMICONDUCTOR DEVICE

A method of manufacturing a semiconductor device includes forming a preliminary source structure including a source sacrificial layer and an upper source layer, forming a hole in the preliminary source structure, forming a preliminary memory layer on a surface of the hole, forming a channel layer on the preliminary memory layer, forming a trench passing through the upper source layer, forming a first buffer pattern by performing a surface treatment on a side portion of the upper source layer exposed by the trench, forming a cavity exposing a portion of the preliminary memory layer by removing the source sacrificial layer, forming an expanded cavity exposing a portion of the channel layer by removing the portion of the preliminary memory layer, and forming a source layer in the expanded cavity.