InSb films were grown on Si(001) substrates covered with Ge islands at 250-400 degrees C by molecular beam epitaxy (MBE), and characterized by reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD) and optical microscope. The Ge islands were formed on Si(001) substrates by the Ge deposition of about 100 monolayers (ML) at 450 degrees C. For the subsequent growth of InSb, two deposition procedures were used. The first is the one-step growth, where the substrate was held at a constant temperature in the 250-100 degrees C range throughout the InSb deposition. The second is the two-step growth, where the substrate temperature was first held at 200 degrees C and subsequently increased to 400 degrees C during the InSb deposition. In the case of one-step growth, the intensity of the InSb(004) peak in the XRD pattern was enhanced with an increase in the growth temperature up to about 300 degrees C, but it decreased for further increases in the temperature. Surface morphology of the films was degraded with an increase in the growth temperature. On the other hand, in the case of two-step growth, the XRD intensity ratio of the intensity of the InSb(004) peak to that of the sum of ail InSb(hkl) peaks of the film improved to about 100%, indicating the heteroepitaxial growth of InSb. The two-step growth was also effective in improving the surface morphology.