Strain relaxation phenomena of the heteroepitaxial lattice-mismatched semiconductors have been investigated. The relationship between the residual in-plane strain and the width of the misfit cell was obtained geometrically. The residual in-plane strain was calculated for various film thicknesses by using the energy minimization theory on the misfit cell in the InxGa1-xAs/GaAs(1 0 0) heterostructure system. A generalized strain relaxation model is presented on the basis of the energy minimization theory. (C) 1999 Elsevier Science B.V. All rights reserved.