A display device may include a substrate, a first layer on the substrate, the first layer including a first portion having a first thickness and a second portion having a second thickness greater than the first thickness, a second layer on the first layer, an active pattern on the second layer, the active pattern overlapping only the first portion of the first layer, a gate electrode on the active pattern, a source electrode and a drain electrode on the gate electrode and connected to the active pattern, a first electrode connected to one of the source electrode and the drain electrode, a pixel defining layer on the first electrode, the pixel defining layer having an opening portion exposing at least a portion of the first electrode, an emission layer in the opening portion on the first electrode, and a second electrode on the emission layer.