A method to produce high-quality low-cost silicon on an insulator is presented. It is based on high-dose helium implantation to form bubbles which evolve by thermal processes in a continuous buried void layer. This layer is therefore oxidised in dry O 2 while oxygen flows in the network through trenches etched deeper than the void layer. By this method defect-free silicon single crystal layers have been obtained. The criteria to produce a void network are discussed considering the helium-implanted ion dose, energy and the subsequent thermal processes. Oxidation in dry O 2 at different temperatures and for different times has been investigated and transmission electron microscopy on cross sectional samples has been used to characterise the quality of the buried oxide layers.