Semiconductor devices including two-dimensional (2D) materials and methods of manufacturing the semiconductor devices are provided. A semiconductor device may include a semiconductor layer including layers of a 2D material, and an intercalation material between the layers of the 2D material. The semiconductor device may further include a first conductive layer on a first surface of the semiconductor layer and a second conductive layer on a second surface of the semiconductor layer that is opposite the first surface. A portion of the 2D material may have a first crystalline structure, and another portion of the 2D material may have a second crystalline structure that is different from the first crystalline structure. The 2D material may include a metal chalcogenide-based material.