A method of manufacturing a display device may include sequentially forming a first conductive layer, a second conductive layer including copper (Cu), a third conductive layer, and a fourth conductive layer on a substrate, patterning the first conductive layer, the second conductive layer, the third conductive layer, and the fourth conductive layer together to form a conductive pattern including a first layer, a second layer, a third layer, and a fourth layer sequentially on the substrate, removing the fourth layer of the conductive pattern, forming a protective layer covering at least a sidewall of the conductive layer on the substrate, and forming a display element on the protective layer.