A TFT array substrate includes a semiconductive oxide layer disposed on an insulating substrate and including a channel portion, a gate electrode overlapping the semiconductive oxide layer, a gate insulating layer interposed between the semiconductive oxide layer and the gate electrode, and a passivation layer disposed on the semiconductive oxide layer and the gate electrode. At least one of the gate insulating layer and the passivation layer includes an oxynitride layer, and the oxynitride layer has a higher concentration of oxygen than that of nitrogen in a location of the oxynitride layer closer to the semiconductive oxide layer.