Manufacturing a semiconductor device by means of molecular beam epitaxy.

Molecular beam epitaxy can be employed to produce a semiconductor layer on a substrate. Etching of the substrate may be necessary to prepare it for the epitaxy process, and a protective layer may advantageously be provided over the semiconductor layer after formation thereof by the epitaxy process. Such a subsidiary process of etching or protective-layer formation is desirably carried out under a vacuum. Steps are taken to ensure that the substrate is maintained under vacuum during the epitaxy process and each such subsidiary process without any break in the vacuum between those processes, thereby reducing the danger of impurities entering the said semiconductor layer. For such etching a hydrogen plasma etching process is employed, thereby avoiding damage that could otherwise be caused to the substrate and to a vacuum pump.