Provided are a field effect transistor, a logic circuit including the same and methods of manufacturing the same. The field effect transistor may include an ambipolar layer that includes a source region, a drain region, and a channel region between the source region and the drain region, wherein the source region, the drain region, and the channel region may be formed in a monolithic structure, a gate electrode on the channel region, and an insulating layer separating the gate electrode from the ambipolar layer, wherein the source region and the drain region have a width greater than that of the channel region in a second direction that crosses a first direction in which the source region and the drain region are connected to each other.