Amorphous boron carbonitride (a-BCN) thin films were deposited by reactive radiofrequency (RF) sputtering onto silicon and glass substrates, from a boron carbide target in an atmosphere composed of a mixture of argon and nitrogen. The a-BCN films were highly transparent (almost 85%) in the visible and near-infrared regions. The optical band gap and the refractive index in the near-infrared region of the a-BCN films were found to be, respectively, in the range of 3.6 and 1.68 eV. The electrical characterization of the a-BCN films for application as an intermetal dielectric was investigated by measuring the current–voltage characteristic in Al/a-BCN/n-Si/Al structure. The electrical resistivity at room temperature, determined in the low voltage region where the Ohmic conduction mechanism is dominant, is around 2 × 1010 Ω cm. The electrical conduction results, in the high-applied fields, were interpreted in terms of a Schottky mechanism. The dielectric constant is about 2.83 and is consistent with the optical results.