| 摘要 |
PURPOSE:To enable an etching process in an ordinary vessel to be performed easily by a method wherein a solution for selective etching and another solution for unselective etching are alternately used to perform partial etching process. CONSTITUTION:An element material 100 is immersed in a HF+H2O2 solution contained in a specified vessel and then the section thickness 10 of a part corresponding to an opening 1a of mask pattern is decreased by unselective etching down to a GaAs film 4. Next, the etched element material 100 is picked out of the vessel; a mask 1 is replaced with a mask pattern 1' with openings 1a, 1b; the element material 100 is immersed in NH4OH+H2O2 solution for selective etching of GaAs; and GaAs films 2, 4 are etched at the parts corresponding to the openings 1a, 1b respectively down to the surface of A GaAs films 3, 5. Through these procedures, the parts corresponding to the openings 1a, 1b of mask 1 are respectively etched down to different depths to form respective gates.
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