A method and apparatus for depositing a material layer onto a substrate is described. The method includes placing the substrate in a process chamber, delivering a mixture of precursors for the material layer into the process chamber, delivering a hydrogen gas into the process chamber to improve water-barrier performance of the material layer, controlling the temperature of the substrate to a temperature of about 100.degree. C. or lower, applying an electric field and generating a plasma inside the process chamber, and depositing the material layer on the substrate. The material layer can be used as an encapsulating layer for various display applications which require low temperature deposition process due to thermal instability of underlying materials used. The encapsulating layer thus deposited provides reduced surface roughness, improved water-barrier performance which can be applied to any substrate type including wafer, glass, and plastic film (e.g., PET, PEN, etc.) and any substrate size in the flat panel industry.