Silicon carbonitride thin films have been deposited by plasma enhanced chemical vapor deposition (PECVD) from bis(dimethylamino) dimethylsilane (BDMADMS) as a function of X=(BDMADMS/(BDMADMS+NH3)) between 0.1 and 1, and plasma power P (W) between 100 and 400 W. The microstructure of obtained materials has been studied by SEM, FTIR, EDS, ellipsometrie, and contact angle of water measurements. The structure of the materials is strongly depended on plasma parameters; we can pass from a material rich in carbon to a material rich in nitrogen. Single gas permeation tests have been carried out and we have obtained a helium permeance of about 10(-7) mol m(-2) s(-1) Pa-1 and ideal selectivity of helium over nitrogen of about 20. (C) 2010 Elsevier B. V. All rights reserved.