A semiconductor device insulation method involves (a) forming an oxide layer on a semiconductor substrate at a first temperature in a first reaction chamber with an atmosphere comprising a first silicon-containing gas (preferably SiH4) and a cleaning gas (preferably N2O); (b) adjusting to a second temperature while continuously introducing cleaning gas into the chamber; (c) injecting the first gas into the chamber to form a compensation or buffer layer; (d) removing a first buffer layer-coated wafer from the first chamber and introducing it into a second reaction chamber under an atmosphere of nitrogen-containing gas (preferably NH3); (e) injecting a second silicon-containing gas (preferably SiH2Cl2) into the second reaction chamber to form a silicon nitride layer on the buffer layer; (f) structuring the silicon nitride, buffer and oxide layers to expose selected sections for forming a field oxide region; and (g) oxidising the exposed region or providing it with a field oxide using the structured silicon nitride layer as mask.
