The feasibility of using CuCuMg as a gate electrode for a-Si:H thin-film transistors (TFTs) has been investigated in this work. The issue of adhesion between the Cu film and glass substrates has been overcome by introducing the CuCuMg alloy. Furthermore, a wet-etching process of Cu-based gate metal has been proposed by using the copper etchant in the conventional printed circuit boards. The experimental result showed superior performance of a-Si:H TFT with desired electrode taper angle and minimal loss of critical dimension. The a-Si:H TFT exhibited mobility of 0.37 cm2 V s, subthreshold slope of 0.83 Vdec, and Vth of 2.02 V.