A thin film transistor (TFT) circuit device comprises a substrate comprising a major surface; a gate line formed over the substrate and extending in a first direction when viewed in a viewing direction perpendicular to the major surface; an insulating layer formed over the gate line; an electrically conductive line formed over the insulating layer and extending in a second direction when viewed in the viewing direction, the second direction being different from the first direction, the electrically conductive line comprising a source line or a data line; and a semiconductor piece formed over the substrate. The semiconductor piece comprises a portion which is located between the substrate and the gate line and overlaps the gate line and the electrically conductive line at an intersection of the gate line and the electrically conductive line when viewed in the viewing direction.