Abstract: A method of manufacturing a semiconductor device is described in which gaseous material is supplied into a reaction chamber containing a substrate to cause a first epitaxial layer of a first material to grow on the substrate and switching means are then operated to alter within a predetermined period the supply of gaseous material into the reaction chamber to cause a second eitaxial layer of a second material to grow on the first layer. During the predetermined period of radiant heat source is activated to radiantly heat the surface of the first layer so as to smooth the first layer on an atomic level before growth of the second layer is commenced. The radiant heat source may be a laser capable of directing one or more laser pulses at the surface to be radiantly heated.