Structural features, related to epitaxial growth and crystal defect creation in common III-V and Si-Ge materials were investigated by high-resolution x-ray diffraction and Transmission Electron Microscopy. Strong correlations between crystal perfection of epitaxial structures and growth conditions, specified by the initial elastic strain, deposition temperature and growth rate, elastic properties of epitaxial structures and thickness of epitaxial layers, were revealed. The investigations allowed suggest phenomenological model of defect creation in epitaxial structures, specify four different stages of defect creation, preferred crystalline defects, their density and spatial distribution in the volume. The main crystalline defect, responsible for deterioration of crystal perfection and physical properties of epitaxial structures were identified. Correct description of defect creation allows improved growth conditions and design of future devices to avoid/minimize deterioration of physical properties due to initially deteriorated growth conditions.