We have grown a tensile-strained Ge layer on a strain-relaxed compositionally step-graded Ge(1-x)Sn(x) buffer layer using virtual Ge substrates. The degree of strain relaxation along [110] direction of the top Ge(0.945)Sn(0.055) buffer layer is achieved up to 85% and the resultant (110) lattice spacing of the Ge(0.945)Sn(0.055) buffer layer is estimated to be 0.4028 nm. A pseudomorphic Ge layer is successfully grown on the Ge(0.945)Sn(0.055) buffer layer, yielding a tensile strain of 0.68% with respect to the (110) lattice spacing of non-strained Ge. This value exceeds those obtained by other methods based on the thermal expansion coefficient difference and strain-relaxed Ge(1-x)Sn(x) buffer layer directly grown on Si(001) substrates. (C) 2008 Elsevier B.V. All rights reserved.