Silicon nitride films have been deposited using electron cyclotron resonance (ECR) plasma-assisted rf sputter deposition. Variation in composition and electrical properties of the deposited films has been studied. Films with specific resistivity of 10(13) Omega cm and a dielectric constant of 7 have been obtained at a ECR power of 100 W (corresponding to an ion flux of 1 X 10(10) cm(-3)). These films exhibited minimum interface density of 2 x 10(10) eV(-1) cm(-2), and have a critical field of 5 MV/cm. Detailed electrical characterization of the films has been carried out to study the variation of interface density with ECR power and to identify the conduction mechanism.