Semiconductor device and method for manufacturing the same

A semiconductor device comprising:

• a pixel portion including a first thin film transistor;
• and
• a driver circuit portion including a second thin film transistor,
• wherein the pixel portion and the driver circuit portion are formed over a substrate,
• wherein the first thin film transistor includes, over the substrate:
• a first source electrode layer,
• a first drain electrode layer,
• an oxide semiconductor layer formed so as to be electrically connected to the first source electrode layer and the first drain electrode layer,
• a gate insulating layer formed so as to cover the oxide semiconductor layer,
• a first gate electrode layer provided over a region of the gate insulating layer, which overlaps with the oxide semiconductor layer,
• a protective insulating layer formed so as to cover the first gate electrode layer, and
• a pixel electrode layer over the protective insulating layer,
• wherein the first source electrode layer, the first drain electrode layer, the oxide semiconductor layer, the gate insulating layer, the first gate electrode layer, the protective insulating layer, and the pixel electrode layer of the first thin film transistor have a light-transmitting property,
• wherein a second gate electrode layer of the second thin film transistor is covered with the protective insulating layer, and
• wherein a second source electrode layer, a second drain electrode layer, and the second gate electrode layer of the second thin film transistor are formed using a stack of a film containing the same material as the first source electrode layer, the first drain electrode layer, and the first gate electrode layer of the first thin film transistor;
• and a film containing a conductive material with lower resistance than the first source electrode layer, the first drain electrode layer, and the first gate electrode layer of the first thin film transistor.