X-ray triple-axis diffractometry (XRTD) was used to characterize heterostructure Si/SiGe/Si on silicon-on-insulator (SOI) subjected to in situ low-temperature annealing. Crystallographic tilt, lattice constant and relaxation percentage were examined, respectively. Two peaks have been observed in (0 0 4) reciprocal lattice mappings (RLMs) of Si layers. The (0 0 4) RLMs indicate that Si cladding is in tensile strain. We have also found two peaks with different k(parallel to) and k(perpendicular to) in (113) asymmetric RLMs of Si layers. It is deduced from comprehensive analyses on (004) and (113) RLMs that Ge diffusion and in-plane tensile strain lead to 2 theta shift of the Si layers underneath SiGe layer in (0 0 4) RLMs. And the diffusion concentration of Ge accurately determined by XRTD is mole fraction 0.84%. (c) 2006 Elsevier B.V All rights reserved.