A semiconductor device includes a first fin structure disposed on a substrate. The first fin structure extends in a first direction. A first sacrificial layer pattern is disposed on the first fin structure. The first sacrificial layer pattern includes a left portion and a right portion arranged in the first direction. A dielectric layer pattern is disposed on the first fin structure and interposed between the left and right portions of the first sacrificial layer pattern. A first active layer pattern extending in the first direction is disposed on the first sacrificial layer pattern and the dielectric layer pattern. A first gate electrode structure is disposed on a portion of the first active layer pattern. The portion of the first active layer is disposed on the dielectric layer pattern. The first gate electrode structure extends in a second direction crossing the first direction.