Auger electron spectroscopy (AES) depth profiles of the interfacial SiO2 and SiO2/Si3N4 layers formed between Ta2O5 film and Si substrate were quantitatively analyzed and the accuracy of the AES analysis was confirmed using a high-resolution cross-sectional transmission electron microscopy (TEM). It has been shown that the AES depth profiling technique is a convenient method for quantitative analysis of the ultrathin interfacial layers, enabling discrimination of the amorphous layers, SiO2/Si3N4.