The structural parameters (the layer thickness, interface roughness) for a 16-period (SinGem) superlattice grown by solid source molecular beam epitaxy (MBE) on Si(001) substrates were determined by high-resolution X-ray diffraction (HRXRD), X-ray reflectivity (XRR) and cross-sectional transmission electron microscopy (XTEM). The results were compared to the data obtained by ultra-low energy secondary ion mass spectrometry (ULE SIMS) method, using a 280 eV O-2(+) probe at 20 degrees to normal incidence. The differences in layer thickness values obtained from HRXRD, XRR and XTEM, ULE SIMS data, are explained in terms of significant microroughness at both the Si/Ge and Ge/Si interfaces. The n and m values were also determined by X-ray diffraction methods.