A multilayered structure of SiOx and SiOxCy on silicon substrate was prepared by plasma-enhanced chemical vapor deposition from gas mixtures of hexamethyldisiloxane and oxygen. Scanning transmission electron microscopy studies showed that the structure is well defined with distinct layers. The distributions of Si, C, and O were measured via electron energy-loss spectroscopy. We found that the elements C, Si, and O interdiffuse quite differently across the interfaces. The Si–L2,3 energy-loss near-edge structures in the SiOx and SiOxCy layers were different from those of pure Si, SiC, and Si3N4, which all contain a tetrahedral structure unit. Slight variations of the relative ratio of the first two sharp peaks at about 108 and 115 eV were found, which can probably be attributed to C partially substituting O atoms in the Si–O tetrahedral structure.