Active matrix substrate and liquid crystal display device

An active matrix substrate having a display region defined by a plurality of pixel regions arrayed along a first direction and a second direction perpendicular to the first direction, the active matrix substrate comprising:

• a substrate;
• a thin film transistor supported by the substrate, the thin film transistor including:
• a lower gate electrode provided on the substrate and made of a lower gate metal layer,
• a lower gate insulating layer covering the lower gate electrode,
• an oxide semiconductor layer provided on the lower gate insulating layer, the oxide semiconductor layer including a channel region opposing the lower gate electrode with the lower gate insulating layer interposed therebetween and a source contact region and a drain contact region located on respective sides of the channel region,
• an upper gate insulating layer provided on the channel region of the oxide semiconductor layer, and
• an upper gate electrode provided on the upper gate insulating layer, made of an upper gate metal layer, and opposing the channel region of the oxide semiconductor layer with the upper gate insulating layer interposed therebetween,
• a lower gate line extending in the first direction, made of the lower gate metal layer, and electrically coupled with the lower gate electrode, and
• an upper gate line extending in the first direction, made of the upper gate metal layer, and electrically coupled with the upper gate electrode,
• wherein a width of the upper gate line is greater than a width of the lower gate line, and
• the lower gate line overlaps with the upper gate line in a plan view.