Thin-film transistors (TFTs) on glass substrates were fabricated using ZnO, grown by a metallorganic chemical vapor deposition (MOCVD) technique, with N- and Si-rich silicon nitrides as gate dielectrics. This is a report on MOCVD-grown ZnO TFTs that use silicon nitride as gate dielectrics. The ZnO TFTs using N-rich silicon nitride exhibited a field-effect mobility of 6.5 cm(2)/V s, a subthreshold slope of 0.8 V/decade, an on/off current ratio of 10(8), and a threshold voltage of 2.05 V. The performance of these TFTs is better than that of TFTs employing Si-rich silicon nitride. This enhanced device performance can be attributed to a larger average grain size of 126 nm observed in the ZnO film grown on the N-rich silicon nitride compared to an average grain size of 69 nm for the ZnO film grown on Si-rich silicon nitride. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3247345] All rights reserved.