In a semiconductor device and a method of manufacturing the same, a conductive structure is formed on an active region defined by a device isolation layer on a semiconductor substrate. The conductive structure includes a gate pattern and source/drain regions adjacent to the gate pattern. A first semiconductor layer is formed on the active region by a selective epitaxial growth (SEG) process. An amorphous layer is formed on the first semiconductor layer. A second semiconductor layer is formed from a portion of the amorphous layer by a solid-phase epitaxy (SPE) process. Elevated structures are formed on the source/drain regions by removing a remaining portion of the amorphous layer from the substrate, so the elevated structure includes the first semiconductor layer and the second semiconductor layer stacked on the first semiconductor layer. The device isolation layer may be prevented from being covered with the elevated structures, to thereby prevent contact failures.