PURPOSE: To enable the FET to be provided with excellent characteristics, precision etc., for more rapid operation.

CONSTITUTION: In the junction type FET, a source 41, a drain 42 and a channel regions 3 are formed of the first conductivity type the first semiconductor while the second conductor 48 in the second conductivity type opposite to the first conductivity type comes into contact with the channel region 3 so as to compose a gate part. On the other hand, the first conductor is formed of compound semiconductor e.g. GaAs etc., for rapid operation and the compound semiconductor is formed by doping with the first conductivity type impurities (e.g. n type impurities) while the second semiconductor 48 is formed by doping hydrogenated amorphous silicon (α-Si:H) as a well know wide band gap semiconductor with the second conductivity type impurities (e.g. p+type impurities).