A low-temperature metallic-zinc-target reactive sputtering technology is used to fabricate a ZnO thin-film transistor (TFT). The effect of the $hbox{O}_{2}/hbox{Ar}$ flow rate ratio on the performance of the resulting TFTs is investigated in detail. It is found that an $hbox{O}_{2}/hbox{Ar}$ ratio of 0.75–0.8 produces devices with the best performance. The maximum processing temperature used in this brief is 150 $^{circ}hbox{C}$, and the fabricated TFTs have a saturation mobility of 7.4 $hbox{cm}^{2}/(hbox{V}cdot hbox{s})$, an on–off current ratio of more than $hbox{1} times hbox{10}^{7}$ , and a subthreshold swing of 0.58 V/dec. Experimental results also show that using $hbox{SiO}_{x}$ as gate dielectric instead of $hbox{SiN}_{x}$ can improve both carrier mobility and subthreshold.