Production of GaAs enhancement and depletion mode HEMT's

摘要

A semiconductor device, which comprises an E-mode FET and a D-mode FET and utilizes a two-dimensional electron gas, comprises a semi-insulating semiconductor substrate (1), a channel layer (2), an electron-supply layer (3), a third layer (4), a first etching-stoppable layer (5), a fifth layer (6), and a second etching-stoppable layer (7), which layers are formed in sequence on the substrate (1). An etching process for forming grooves (22E, 22D, 45E, 45D) of gate electrodes (23, 24, 46, 47) of the FET's comprises a first etching treatment removing the first etching-stoppable layer portion (5) in the E-mode FET region and the second etching-stoppable layer portion (7) in the D-mode FET region, and a second etching treatment removing the third layer portion (4) in the E-mode FET region and the fifth layer portion (6) and using an etchant different from that used in the first etching treatment. In the second etching treatment, reactive ion etching method using a CC12F2 etchant gas is adopted, since GaAs can be thereby rapidly etched as compared with AlGaAs used for the etching-stoppable layer material.