A copper gate electrode, applied in a thin-film-transistor liquid crystal display (LCD) device, at least comprises a patterned copper layer formed on a glass substrate, and a barrier layer formed on the patterned copper layer. The barrier layer comprises at least one of nitrogen and phosphorus, or comprises an alloy formularized as M.sub.1M.sub.2R wherein M.sub.1 is cobalt (Co) or molybdenum (Mo), M.sub.2 is tungsten (W), molybdenum (Mo), rhenium (Re) or vanadium (V), and R is boron (B) or phosphorus (P).