Semiconductor device and method for manufacturing the same

A semiconductor device comprising:

• a pixel portion over a substrate, the pixel portion including a first transistor;
• and
• a driver circuit portion over the substrate, the driver circuit portion including a second transistor,
• wherein the first transistor includes:
• a first gate electrode layer over the substrate;
• a gate insulating layer over the first gate electrode layer;
• a first oxide semiconductor layer over the gate insulating layer;
• a first source electrode layer and a first drain electrode layer over the first oxide semiconductor layer;
• a first conductive layer on and in contact with a part of the first source electrode layer or a part of the first drain electrode layer;
• a first oxide insulating layer over the gate insulating layer, the first oxide semiconductor layer, the first source electrode layer, and the first drain electrode layer, the first oxide insulating layer being in contact with at least a part of the first oxide semiconductor layer between the first source electrode layer and the first drain electrode layer, and
• a pixel electrode layer over the first oxide insulating layer, the pixel electrode layer electrically connected to the first conductive layer,
• wherein the second transistor includes:
• a second gate electrode layer over the substrate;
• the gate insulating layer over the second gate electrode layer;
• a second oxide semiconductor layer over the gate insulating layer;
• a second source electrode layer and a second drain electrode layer over the second oxide semiconductor layer;
• and
• a second oxide insulating layer over the second oxide semiconductor layer, the second source electrode layer and the second drain electrode layer, the second oxide insulating layer being in contact with the second oxide semiconductor layer,
• wherein each of the first gate electrode layer, the gate insulating layer, the first oxide semiconductor layer, the first source electrode layer, the first drain electrode layer, the first oxide insulating layer, and the pixel electrode layer includes light-transmitting properties,
• wherein a material of the second source electrode layer and the second drain electrode layer is different from a material of the first source electrode layer and the first drain electrode layer, and
• wherein the material of the second source electrode layer and the second drain electrode layer is a conductive material having a lower resistance than the material of the first source electrode layer and the first drain electrode layer.