A display device includes a first signal line including a first layer disposed on a substrate and containing aluminum (Al), a second layer disposed on the first layer and containing titanium nitride (TiNx), and a third layer disposed on the second layer and containing titanium (Ti), a second signal line crossing the first signal line, a first transistor including a first gate electrode connected to the first signal line and a first source electrode connected to the second signal line, and an organic light emitting diode disposed in a display area of the substrate to generate light corresponding to a data signal applied to the second signal line.