Silicon nitride (SiNx) and silicon oxynitride (SiOxNy) films have been formed by catalytic chemical vapor deposition (Cat-CVD) method using hexamethyldisilazane (HMDS). Addition of NH3 gas and increase in gas pressure can prevent carbonization of tungsten (W) catalyzer. These SiOxNy films have high gas barrier ability compare to the case of SiOxNy films using SiH4 and thus are expected for novel sealing films. (C) 2007 Elsevier B.V. All rights reserved.