contamination, oxidization and radiation damage are induced on a gaas surface by reactive ion etching (rie) using a o/sub 2/-discharge of 13.56 mhz in a parallel plate reactor. this formation depends on several rie conditions, such as rf power (which is equivalent to cathode-accelerated voltage) and etching time. the increase in schottky junction leakage current and the decrease in the schottky barrier height are caused by the induced damage which extends to a depth of 0.2 mu m from the surface. the damage thus induced compensates by more than 1*10/sup 16/ cm/sup -3/ the carrier concentration in gaas. as a result, dc characteristics of mesfets such as i/sub dss/, gm and vp, decrease. it has been confirmed that several methods, such as the protection of the gaas surface by a sio/sub 2/ layer, wet etching of the gaas surface and thermal annealing after dry etching under low cathode accelerated voltage conditions, are useful techniques for surface treatment in the fabrication of gaas mesfets without damage influence