A field effect transistor includes a substrate, a source electrode and a drain electrode on the substrate and apart from each other in a first direction, a plurality of channel layers, a gate insulating film surrounding each of the plurality of channel layers, and a gate electrode surrounding the gate insulating film. Each of the plurality of channel layers has ends contacting the source electrode and the drain electrode. The plurality of channel layers are spaced apart from each other in a second direction away from the substrate. The plurality of channel layers include a 2D semiconductor material.