Silicon nitride (SiN) film was deposited at 300 degreesC as the insulating layer of a GaN-based metal-insulator-semiconductor (MIS) diode by using electron cyclotron resonance chemical vapor deposition (ECR-CVD) with silane-to nitrogen (SiH4/N-2) flow ratio of 5/45. The deposited film had the refractive index of 1.9-2.0 and the relative dielectric constant of 6. Capacitance-voltage (C-V) characteristics were measured at I MHz and interface state densities were obtained by Terman's method. The negative fixed charge density of the SiN film was 1.1 x 10(11) cm(-2) and its breakdown field was greater than 5.7 MV/cm even at 350 degreesC. The value of the interface state density was less than 4 x 10(11) cm(-2) around the mid-gap and its minimum was 5 x 10(10) cm(-2) eV(-1) at 0.6 eV below the conduction band edge. From these results, the SiN film deposited by ECR-CVD is a promising gate dielectric for high temperature GaN-MISFET application. (C) 2002 Elsevier Science Ltd. All rights reserved.