Provided herein is a semiconductor device including N stacked groups (where N is a natural number greater than or equal to two) sequentially stacked over a substrate, each stacked group including interlayer insulating films and conductive patterns alternately stacked, and N concave portions each having stepped sidewalls formed in the interlayer insulating films and the conductive patterns of the stacked groups, the N concave portions each having stepped sidewalls being aligned in a first direction.