A semiconductor device, a field effect transistor, and a fin field effect transistor are provided. The semiconductor device may include a channel layer, a source/drain layer, and a gate electrode. The channel layer is provided on a substrate and extends in a direction perpendicular to a top surface of the substrate. The source/drain layer is disposed at a side of the channel layer and is electrically connected to the channel layer. The gate electrode is provided adjacent to at least one of surfaces of the channel layer. The channel layer includes a two-dimensional atomic layer made of a first material.