Disclosed are semiconductor devices including support patterns and methods of fabricating the same. The semiconductor devices may include a plurality of vertical structures on a substrate and a support pattern that contacts sidewalls of the plurality of vertical structures. The support pattern may include a plurality of support holes extending through the support pattern. The plurality of support holes may include a first support hole and a second support hole that are spaced apart from each other, and the first support hole may have a shape or size different from a shape or size of the second support hole.