A thin-film transistor substrate may include an electrical wiring structure that includes a first electrode, which may be a source electrode, a drain electrode, or a capacitor electrode. The thin-film transistor substrate may further include a first insulating layer that directly contacts a first side of the first electrode. The thin-film transistor substrate may further include a second insulating layer that directly contacts a second side of the first electrode opposite the first side of the first electrode. The thin-film transistor substrate may further include a first filling layer that is disposed between the first insulating layer and the second insulating layer.