Almost fully relaxed thin SiGe buffer layers are obtained by At ion implantation into Si substrates before SiGe molecular beam epitaxy (MBE) growth. The strain relaxation ratio of the 100 nm thick Si0.65Ge0.35 layer grown on ion implanted Si substrate is about 95%, while it is only 60% in the unimplanted case. Surface morphology of the buffer layer on the implanted Si is very different from that of the conventional buffer, suggesting that a new strain relaxation mechanism takes place in the SiGe film grown on the ion implanted Si. (C) 2003 Elsevier B.V. All rights reserved.