He ion implantation into Si/SiGe heterostructures and annealing are used to produce strain-relaxed SiGe layers and simultaneously thin strained Si layers. In addition we present various studies of subsequent epitaxial overgrowth by chemical vapor deposition. Up to a thickness of 8 nm strained Si on relaxed SiGe virtual substrates are made by strain transfer via dislocation propagation. An initial cubic-Si/strained-SiGe/Si(100) structure is transformed by He+ ion implantation and annealing into strained-Si/pdartially relaxed-SiGe/Si(100). These layers show low threading dislocation densities and very smooth surfaces. Such virtual substrates were overgrown with Si to achieve 20 nm of strained Si. A tensile strain of 0.8% was measured by Raman spectroscopy for an 18.5 nm sSi layer with a surface roughness of only 0.8 nm measured by AFM. The threading dislocation density was reduced by overgrowth of an additional strain adjusted SiGe layer and sSi layer. (c) 2005 Elsevier Ltd. All rights reserved.