Low-dielectric constant SiOC(H) films were deposited on p-type Si(100) substrates using plasma enhanced chemical vapor deposition (PECVD) at different radio frequency (rf) powers. The structural characteristics of the SiOC(H) films were characterized using Fourier transform infrared spectroscopy (FTIR) in the absorbance mode. The bonding configurations of the SiOC(H) films remained unchanged upon annealing, showing their good thermal stability. Electrical characteristics of the SiOC(H) thin films with Al/SiOC(H)/p-Si(100)/Al metal-insulator-semiconductor (MIS) structures were analyzed using capacitancevoltage (CV) and conductancevoltage (G/ωV) at different frequencies. The conductance and the capacitance measurements were used to extract the interface state density in the MIS structures. From the experimental data and the subsequent quasi-static CV analysis, the energy distribution of interface state density was obtained. The interface state density of the as-deposited and 400°C annealed MIS structures increased with increasing rf powers, whereas the fixed charge density decreased with increasing rf powers. The interface state densities and their electrical properties of the SiOC(H) films strongly affected by the radio frequency power. © 2012 Elsevier Ltd. All rights reserved.