A semiconductor device includes a channel layer protruding from a substrate and having protrusions extending from a sidewall thereof. Floating gates surrounding the channel layer are provided between the protrusions. Control gates surrounding the floating gates are stacked along the channel layer. Interlayer insulating layers are interposed between the control gates stacked along the channel layer. A level difference exists between a lateral surface of each of the floating gates, and a lateral surface of each of the protrusions.