Display device and manufacturing method thereof

A display device comprising:

• a first conductive layer over a substrate, the first conductive layer extending in a first direction;
• a second conductive layer over the substrate, the second conductive layer extending in the first direction;
• a first insulating layer over the first conductive layer and the second conductive layer;
• a second insulating layer over the first insulating layer;
• a semiconductor layer over the second insulating layer, the semiconductor layer comprising a first semiconductor film having a first thickness and a second semiconductor film having a second thickness larger than the first thickness;
• a third conductive layer and a fourth conductive layer over and electrically connected to the semiconductor layer;
• a third insulating layer over the third conductive layer and the fourth conductive layer;
• a fifth conductive layer overlapping with the second conductive layer;
• and
• a pixel electrode electrically connected to a transistor via a first contact hole,
• wherein the first conductive layer comprises a region functioning as a gate electrode of the transistor,
• wherein the third conductive layer comprises a region functioning as one of a source electrode and a drain electrode of the transistor,
• wherein the fourth conductive layer comprises a region functioning as the other of the source electrode and the drain electrode of the transistor,
• wherein the pixel electrode comprises a plurality of slits,
• wherein the second conductive layer overlaps with one of the plurality of slits,
• wherein the fifth conductive layer does not overlap with the plurality of slits,
• wherein the second conductive layer and the fifth conductive layer are electrically connected to each other via a second contact hole,
• wherein each of the third conductive layer and the fourth conductive layer comprises titanium or titanium nitride, and
• wherein each of the first semiconductor film and the second semiconductor film comprises indium, gallium, and tin.