In this work, we present a study on the growth of a-SiOx, on 4H-SiC wafers by plasma enhanced chemical vapor deposition (13.56 MHz) at a temperature of approximately 300 degreesC, using SiH4 and CO2 as precursor gases in H-2 dilution, obtaining a growth rate of approximately 1.5 Angstrom s(-1). The silicon oxide layers were analyzed by optical spectroscopy, to evaluate the band gap of the material; moreover, electrical measurements were performed to check the breakdown voltage and oxide electrical quality. The results show an a-SiOx material with physical properties comparable to the ones of thermally grown SiO2. A thermal process in oxidizing atmosphere was performed on some samples after the growth of the films in order to reduce the density of oxide charge. The a-SiOx films were used as insulating layers for the realization of Schottky diodes based on 4H-SiC.