METHOD OF PRODUCING FIELD EFFECT TRANSISTOR

A method for the fabrication of gallium arsenide (GaAs) metal-semiconductor field effect transistor (MESFET) is described. The method requires the step of providing a semi-insulating GaAs substrate (10) having thereon a layer of n doped GaAs (24) and another layer of n+ doped Ga1-xAlxAs (not shown), the latter being used as a diffusion source for n dopants in selectively doping the n GaAs layer underneath to form source and drain regions (22. 24). The fabrication method further includes the step of employing highly directional reactive ion etching on silicon nitride to build insulating side walls 18, 20 to effect the self-alignment of the gate of the MESFET with respect to its source and drain.