Strain relaxation behaviors of the epitaxial CoSi2 (epi-CoSi2) and Si0.83Ge0.17 layers in epi-CoSi2/Si0.83Ge0.17/Si(0 0 1) and cap-Si/Si0.83Ge0.17/Si(0 0 1) structures were investigated by high-resolution X-ray diffraction (HR-XRD) analyses. Samples were treated at the temperature, T-A = 650-900 degreesC by rapid thermal annealing. Comparative measurements showed a different strain relaxation behavior in the SiGe layers with and without COSi2 layer. And Ge content and lattice mismatch in the SiGe film of the epi-CoSi2/Si0.83Ge0.17/Si(0 0 1) are smaller than those in the SiGe layer in cap-Si/SiGe/Si(0 0 1) possibly due to the diffusion of Ge into the tensile-stressed epi-CoSi2 layer to reduce the compressive stress in the SiGe layer at elevated temperature. The analyses of high-resolution omega-2theta scan spectra and reciprocal space mapping showed that epi-CoSi2 layer is under tensile residual stress and a significant strain relaxation starts at T-A = 900 degreesC indicating of thermal stability up to TA 850 degreesC. (C) 2004 Elsevier B.V. All rights reserved.