It is demonstrated that Raman spectroscopy is a powerful tool to characterize interface regions of semiconductor heterostructures with lattice misfit. Depth profiles of residual strain in thick heteropitaxial layers are obtained by micro-Raman technique. The results show that considerable misfit strain remains near the interface in heterolayers whose average strain is almost null. This indicates that the relaxation is not completed at the interface but proceeds gradually away from the interface. The very early stage of the crystal growth and lattice relaxation is investigated by Raman measurement of ultrathin heterolayers. Layers as thin as 1nm-thick are successfully characterized, and the critical thickness of the onset of dislocation nucleation is determined. In addition, the effect of interface defects on the phonon coupling between the hetrolayers and the substrate are discussed.