Beveled SIMOX (separation by implanted oxygen) samples obtained by different processes have been analyzed by Raman scattering and Fourier transform infrared (FTIR) reflection-absorption spectroscopy techniques. In both cases, measurements have been made with a microscope, which made it possible to directly observe the different regions of the silicon and buried oxide layers on the structures. Micro-Raman measurements performed with an excitation wavelength of 457.9 nm (penetration depth of about 300 nm) show the existence of structural differences in the Si regions of the different samples, related to the technological processes. The structural characterization of the buried oxides has been carried out by infrared (IR) microscope reflection measurements. A comparison of the characteristics of the TO₃-LO₃ and TO₄-LO₄ vibrational peaks in the IR spectra gives information about the structural characteristics of the oxides