A field effect transistor comprising: a semiconductor layer projecting from the plane of a base; a gate electrode provided on opposite side surfaces of the semiconductor layer; a gate insulating film interposed between the gate electrode and the side surface of the semiconductor layer; and source/drain regions where a first conductivity type impurity is introduced, wherein the semiconductor layer has a channel forming region in a portion sandwiched between the source/drain regions, and has in the upper part of the semiconductor layer in the channel forming region a channel impurity concentration adjusting region of which the concentration of a second conductivity type impurity is higher than that in the lower part of the semiconductor layer, and in the channel impurity concentration adjusting region, a channel is formed in a side surface portion facing the gate insulating film of the semiconductor layer in the channel impurity concentration adjusting region in a state of operation in which a signal voltage is applied to the gate electrode.