We report the effect of low temperature long anneals on the performance and elevated temperature stability of low temperature fabricated indium zinc oxide (IZO) thin film transistors (TFTs). There is an optimum annealing time of 48 h for the best performance and elevated temperature stability. The 48 h annealed TFTs showed stable turn-on voltage and subthreshold swing with operation temperatures when compared to the as-fabricated TFTs. The performance/stability improvements are attributed to the reduction in trap-state density at the semiconductor/insulator interface and to the curing of the defect states in the bandgap of IZO. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3487930] All rights reserved.