A semiconductor device may include a first source layer, a first insulating layer located over the first source layer, and a first stacked structure located over the first insulating layer. The semiconductor device may include first channel layers passing through the first stacked structure and the first insulating layer. The semiconductor device may include a second source layer including a first region interposed between the first source layer and the first insulating layer and a second region interposed between the first channel layers and the first insulating layer.