The trap densities (D-t) of ZnO thin-film transistors with SiNx/SiOx stacked gate insulators are extracted, and the dependence on the N2O flow rate during SiOx deposition (R-N2O) is evaluated. The trap states consist of deep flat states and shallow tail states where the deep states are similar, but the tail states vary. Although a previous study indicated the bias stability is superior for R-N2O = 100 sccm, herein D-t is minimal for the same R-N2O. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3601058] All rights reserved.