PURPOSE: To imorove the reverse withstand voltage of a gate electrode, which is provided in a cavity formed in the uppermost active layer, by reducing electrostatic focusing at the end of a drain electrode.
CONSTITUTION: GaAs base 1, buffer layer 2, and active layer 3 are formed, as laid over each other, by epimerization. Over layer 3 a source electrode 4 and a drain electrode 5 are placed in an integral form. By photographically etching a photoresist 8, an opening 9 is provided, which, as such, is immersed in water at a predetermined temperature for a predetermined period of time. As a result, the side walls of opening 9 peel off layer 3 and rise to the surface of water. Then, the surface of layer 3 is subjected to etching, so that a cavity 7 is formed. A metal layer 10 is provided in cavity 7 by means of evaporation; layer 10 is then transformed to be a gate electrode 6a by lifting resist 8 off. This method enables the length LR of cavity 7 to approximate the length Lg of gate electrode 6a, since the peeling of the side walls of openig 9 can be controlled as desired. As a result, the resistance between electrodes 4 and 6a can be minimized, while electrostatic focusing at the end of drain electrode 5 can be reduced, since cavity 7 is formed apart from the drain, thus finally improving the reverse withstand voltage of gate electrode 6a.
MITSUI YASUROU
WATASE MANABU
KOBIKI MICHIHIRO
MITSUI SHIGERU
