We study the dielectric properties (dielectric constant, loss and leakage current) of SiOC: H (silicon oxycarbide) thin films deposited by plasma-enhanced chemical vapor deposition from trimethylsilane (Dow Corning Z3MS gas precursor). The complex permittivity is studied from 0.01 Hz to 1 MHz as a function of temperature (room temperature to 115degreesC). The conductivity is studied as a function of the electric field, temperature, and time (current transients following application of bias). The films possess a low dielectric constant (around 2.8), which slightly decreases (from 2.88 to 2.82) when the frequency increases from 0.01 Hz to 1 MHz. The temperature dependence of the dielectric constant follows a Debye law (variation with 1/T, Nmu(2) = 4 x 10(-32) C-2 m(-1), epsilon(infinity) = 2.46). Electronic, ionic, and dipolar polarizations contribute 0.93, 0.53, and 0.37 to the dielectric constant, respectively. The loss factor (epsilon") is around 0.006 (dissipation factor tan delta = 0.002). Application of a voltage step leads to current decays which persist up to at least 10(3) s. The current density is very low in these films (a few 10(-11) A/cm(2) at 1 MV/cm). Leakage currents are thermally activated (activation energy of 0.35 eV). (C) 2003 The Electrochemical Society.