Nitrogen-rich amorphous silicon nitride (a-SiNalpha:H) films with [N]/[Si] ratios ranging from 1.4 to 1.7 were deposited by a 13.56 MHz plasma-enhanced chemical vapor deposition method at a temperature of 120degreesC. The films' composition, dielectric constant, electrical resistivity, and breakdown voltage were evaluated. The electrical properties of a-SiNx:H films with a [N]/[Si] ratio of more than 1.6 are superior to their lower N-content counterparts. Amorphous silicon thin film transistors (TFTs) that incorporate a-SiNx:H dielectrics were fabricated on glass and plastic substrates at a maximum processing temperature of 120 degreesC. The TFTs exhibit effective field effect mobility of 0.5-0.8 cm(2)/V s, an ON current of similar to10(-5) A, an ON/OFF ratio of more than 10(6) and a subthreshold slope of 0.5 V/dec. The performance of the transistors seems to be compatible with application of them in active-matrix organic light emitting displays.