In one embodiment, a method of fabricating a semiconductor device having a crystalline semiconductor layer includes preparing a semiconductor substrate and forming a preliminary active pattern on the semiconductor substrate. The preliminary active pattern includes a barrier pattern and a non-single crystal semiconductor pattern. A sacrificial non-single crystal semiconductor layer covers the preliminary active pattern and the semiconductor substrate. By crystallizing the sacrificial non-single crystal semiconductor layer and the non-single crystal semiconductor pattern, using the semiconductor substrate as a seed layer, the sacrificial non-single crystal semiconductor layer and the non-single crystal semiconductor pattern are changed to a sacrificial crystalline semiconductor layer and a crystalline semiconductor pattern, respectively. The crystalline semiconductor pattern and the barrier pattern constitute an active pattern. The sacrificial crystalline semiconductor layer is removed.