We investigated the influence of composite oxides on the electrical property of the Si/SiO2 interface using a high frequency capacitance-voltage (C-V) technique. The composite oxides are composed of inorganic spin-on-glass (SOG) and nondoped silicate glass (NSG) film deposited by atmospheric pressure chemical vapor deposition with a high yield of water absorption. The density of SOG-related positive charge is enhanced about 1.8 times higher by laying the NSG film under the SOG film, while no enhancement is observed by laying it on the SOG film. The enhancement is because the underlying NSG film absorbs water generated by the dehydration of Si(OH), during the SOG curing process. The water-absorbed NSG film seems to increase the amount of atomic hydrogen which generates the positive charge.