| 摘要 |
PURPOSE:To reduce an amount of scatter of FET threshold voltage and enhance a yield rate of GaAs IC by treating an insulated film through an etching process under low gas pressure and causing a semiconductor substrate to be exposed by increasing the gas pressure for etching. CONSTITUTION:An insulated film 4 is formed on the whole surface of semiconductor substrate 1 after forming an active layer 2 on the substrate 1. After an ohmic electrode 5 is formed, a gate electrode pattern 7 is formed according to a resist 6 and the above insulated film 4 is treated by etching after decreasing etching gas pressure through a reactive ion etching device and as a result, the insulated film 4 is left at a gate electrode opening part 8. And then, the reactive ion etching is carried out by increasing etching gas pressure and the insulated film 4 remained at the gate electrode opening part 8 is treated by etching and the treated film 4 allows the substrate 1 to be exposed, resulting in the formation of a gate electrode 10 at the gate electrode opening 9 where the substrate 1 is exposed. For instance, the formation of recessed part 8 of silicon nitriding film 4 necessitates CF4 gas pressure to have 10 Pa and the etching treatment is carried out under gas pressure of 30 Pa until a resultant substrate exposure.
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