Silicon oxide films were prepared on silicon- and quartz-substrate by plasma enhanced chemical vapor deposition (PECVD) technique. The dependence of composition, structure and properties of the films were investigated on the location of substrates in the reaction chamber, namely, which were fixed onto either cathode- or anode-electrode plate. Meanwhile, the preparation of functional decorative silicon oxide films with high transparency and scratch resistance was assessed in terms of processing parameters. The results show that the film synthesized on the substrate attached to anode is organosilicon oxide of Si (CH₃)_nO with transmittance of as high as 90%~98% in the wavelength range of 380-780 nm, unfortunately, the film is loose with hardness of only 2 GPa. However, the hardness of the film can be increased to 6 GPa by increasing the substrate temperature, as a result, the transmittance of the film decreases slightly; The film synthesized on the substrate attached to the cathode composes of inorganic silicon oxide and amorphous carbon. That film is compact with hardness of up to 15 GPa, but poor transmittance in the wavelength range of 380~780 nm. Increasing the O₂-flux can promote the reaction of carbon and oxygen to produce carbon dioxide, thereby to eliminate the amorphous carbon. Therefore, the transmittance of the film increases to 99%, but the hardness decreases down to 9 GPa.