Auger electron spectroscopy in conjunction with simultaneous Argon‐ion sputtering have been used in a study of the chemical depth profiles of the near‐interface regions in MOS and MNOS device structures. Our experimental results show that all of these interfaces are nonabrupt and phase separated. The Al–SiO2interface has inclusions of Si and A12O3; the SiO2–Si interface appears to be a mixed phase of Si and SiO2 over several nanometers and the nitride–oxide interface is an oxynitride. The width of these interfaces varies from 35 to several hundred angstrom, depending on the deposition technique and on the deposition conditions. The inherent limitations in the depth resolution of Auger/sputter profiling are discussed in some detail. We also describe the precautions we have taken to minimize electron and ion beam induced distortion of the Auger spectra and the depth profiles.