A method of fabricating a semiconductor device includes sequentially forming a first pattern and a second pattern on a substrate, the second pattern being a non-single-crystalline semiconductor stacked on the first pattern, wherein a portion of the substrate is exposed adjacent to the first and second patterns, forming a non-single-crystalline semiconductor layer on the substrate, the semiconductor layer contacting the second pattern and the exposed portion of the substrate, and, using the substrate as a seed layer, changing the crystalline state of the semiconductor layer to be single-crystalline and changing the crystalline state of the second pattern to be single-crystalline.