The present disclosure relates to a thin film transistor substrate having two different types of thin film transistors on the same substrate. A thin film transistor substrate includes a substrate; a first thin film transistor disposed on the substrate, the first thin film transistor including a poly crystalline semiconductor layer, a first gate electrode over the poly crystalline semiconductor layer, a first source electrode, and a first drain electrode; a second thin film transistor disposed on the substrate, the second thin film transistor including a second gate electrode, an oxide semiconductor layer over the second gate electrode, a second source electrode, and a second drain electrode; and an intermediate insulating layer including a nitride layer and an oxide layer on the nitride layer, the intermediate insulating layer disposed over the first gate electrode and the second gate electrode and under the oxide semiconductor layer.