PURPOSE: To reduce an OFF current generated when holes exceed a potential barrier if a gate electrode is negatively biased by nitriding the surface of a semiconductor layer and then laminating an ohmic contact layer thereon.
CONSTITUTION: A glass substrate 1 formed with a gate electrode 2 is mounted on a plasma CVD system, and an insulating film 3 is laminated. Then, a semiconductor layer 4 is laminated on the film 3 in the same CVD system. Thereafter, the surface of the layer 4 is plasma nitrided in the same system. Further, an ohmic contact layer is laminated on a nitrided and carbonized or oxidized layer 4a in the same system. The thus treated substrate 1 is removed from the system, and an ohmic contact layer 5 on a channel is removed by photoetching. The substrate 1 is again mounted in the system, and a protective film 6 is formed. Thus, nitrogen, carbon or oxygen is added to the ohmic contact layer, and its energy band gap is extended.
IKEDA NAOKI
KOMAKI KENJI
