MANUFACTURE OF COMPOUND SEMICONDUCTOR FIELD EFFECT TRANSISTOR

PROBLEM TO BE SOLVED: To prevent Au atom from attaching to a GaAs active layer surface by forming a lower layer electrode alone by etching, using a first insulation film as a mask, covering a board surface with a passivation film and forming an upper layer electrode mainly composed of Au on a lower layer gate. SOLUTION: An n-GaAs active layer 2 is formed on a semi-insulating GaAs board, an opening part is formed and a WSi film 4 is processed to a desired shape as a WSi lower layer gate 4'. Then, an SiO2 spacer film 3 is removed by using hydrofluoric acid water solution. After an SiON passivation film 5 is deposited all over and a surface of the GaAs active layer 2 is covered, an opening part is provided and a source electrode 6 and a drain electrode 7 formed of an AuGe metallic film are formed inside an opening part. Since an Au electrode is formed after the SiO2 spacer film 3 is removed by etching, Au does not stick to a surface of a GaAs active layer surface in an etching process and stability of breakdown strength, etc., can be ensured.