Provided is a display device. The display device includes: a substrate; a gate line disposed on the substrate; a transistor including a part of the gate line; and a light-emitting element connected to the transistor, in which the gate line includes a first layer including aluminum or an aluminum alloy, a second layer including titanium nitride, and a third layer including metallic titanium nitride. An N/Ti molar ratio of the metallic titanium nitride may be in a range from about 0.2 to about 0.75.