Semiconductor device and method for manufacturing semiconductor device

A semiconductor device comprising:

• a driver circuit including a first thin film transistor and a pixel including a second thin film transistor over an insulating surface,
• the first thin film transistor comprising:
• a first gate electrode layer over the insulating surface;
• a gate insulating layer over the first gate electrode layer;
• a first oxide semiconductor layer comprising a first channel formation region over the first gate electrode layer with the gate insulating layer therebetween;
• a first oxide conductive layer and a second oxide conductive layer over the first oxide semiconductor layer;
• an oxide insulating layer which is in contact with the first channel formation region and which covers an end portion of the first oxide conductive layer and an end portion of the second oxide conductive layer;
• a first source electrode layer over the oxide insulating layer and in contact with the first oxide conductive layer;
• and
• a first drain electrode layer over the oxide insulating layer and in contact with the second oxide conductive layer;
• and
• the second thin film transistor comprising:
• a second gate electrode layer over the insulating surface;
• a second oxide semiconductor layer comprising a second channel formation region over the second gate electrode layer with the gate insulating layer therebetween;
• and
• a second source electrode layer and a second drain electrode layer over the second oxide semiconductor layer,
• wherein the second gate electrode layer, the second oxide semiconductor layer, the second source electrode layer and the second drain electrode layer each have a light-transmitting property.

A method for manufacturing a semiconductor device, comprising the steps of:

• forming a first gate electrode layer and a second gate electrode layer over an insulating surface;
• forming a gate insulating layer over the first gate electrode layer and the second gate electrode layer;
• forming a first oxide semiconductor layer over the first gate electrode layer with the gate insulating layer interposed therebetween and forming a second oxide semiconductor layer over the second gate electrode layer with the gate insulating layer interposed therebetween;
• performing heat treatment on the first oxide semiconductor layer and the second oxide semiconductor layer in order to decrease a hydrogen concentration in the first oxide semiconductor layer and the second oxide semiconductor layer;
• forming a first oxide conductive layer and a second oxide conductive layer over the first oxide semiconductor layer, and forming a second source electrode layer and a second drain electrode layer over the second oxide semiconductor layer after performing the heat treatment;
• forming an oxide insulating layer over the first oxide conductive layer and the second oxide conductive layer so that the oxide insulating layer is in contact with part of the first oxide semiconductor layer between the first oxide conductive layer and the second oxide conductive layer, and part of the first oxide conductive layer and part of the second oxide conductive layer are exposed;
• and
• forming a first source electrode layer over the first oxide conductive layer, and a first drain electrode layer over the second oxide conductive layer.