A semiconductor device includes a stack structure located on a substrate and includes a first region, in which sacrificial layers and insulating layers are alternately stacked, and a second region, in which conductive layers and insulating layers are alternately stacked. The stack structure also includes a first slit insulating layer located at a boundary between the first region and the second region, wherein the first slit insulating layer penetrates the stack structure and extends in one direction. The stack structure further includes a plurality of slit insulating patterns located in the second region, wherein the plurality of slit insulating patterns penetrate the stack structure and are arranged along the one direction. At least one conductive layer among the conductive layers is bent between the first slit insulating layer and the slit insulating patterns.