We report the influence of a heavy Kr gas sputtering process on the electrical and structural features of amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFFs). Electrical observation revealed effective reduction of threshold voltage shifts by adapting a simple sputtering process with Kr gas during growth of a-IGZO TFTs. In addition, the application of Kr-gas resulted in a reduction of oxygen vacancies associated with defect sites in the a-IGZO active channel layer. Structural analyses including atomic force microscopy, X-ray reflectivity, Auger electron spectroscopy, and X-ray photoelectron spectroscopy depth profiling were carried out, along with electrical bias stability tests that convincingly confirm progress of heavy Kr gas process-induced features. (C) 2015 Elsevier B.V. All rights reserved.