Abstract: Source/drain diffusion regions are formed on the silicon substrate such that the source/drain diffusion regions sandwich a gate electrode from both sides on the silicon substrate. Sidewall oxide films are formed, one on each side surface of the gate electrode. Recessed portions are formed in the extension portions E beneath the sidewall oxide films. Source/drain electrodes are formed to fill the recessed portions. Thus, the sheet resistance of the respective regions including a pair of source/drain diffusion regions and source/drain electrodes is reduced, and a semiconductor device with a field-effect transistor having an improved current drivability is obtained.

Abstract: A semiconductor device includes an n.sup.+ type InGaAs layer at a surface of the device, a refractory metal emitter electrode making ohmic contact to the n.sup.+ layer without alloying, and an externally accessible base region produced in the neighborhood of the emitter electrode by a diffusion using the emitter electrode and an insulating side wall film as a diffusion mask.