Effects of oxygen plasma ashing on barrier dielectric SiCN films have been studied for various ashing conditions. According to X-ray photoelectron spectra analyses, Si - O2 bonds appear at the surface of SiCN film after O2 plasma ashing. The formation of the oxidized layer, SiO xCN, at the surface of the SiCN film effectively reduces the leakage current as a consequence. The leakage conduction of the SiCN films has been investigated to be Schottky emission at the fields between 0.4 and 1.2 MV/cm. Also, the increase of Schottky barrier height between SiCN and the metal is calculated to be 42 meV after O2 plasma ashing. All rights reserved.