Abstract: A field effect transistor is disclosed in which an underlayer has the protrusion wherein the channel is to be formed, and a lower insulating layer is provided on the underlayer around the protrusion. On the upper side of the lower insulating layer, first and second principal electrode region are respectively positioned on the two sides of the protrusion in the length-wise direction of the channel. Parts of the principal electrode regions make a junction with protrusion along the width-wise direction of the channel. On the upper side of the protrusion a gate electrode is provided with a gate insulating therebetween. The principal electrode regions serve as source/drain regions.