Semiconductor device and manufacturing method thereof

A semiconductor device comprising:

• a substrate;
• a driver circuit portion including a first transistor over the substrate;
• a pixel portion including a second transistor and a pixel electrode layer over the substrate;
• and
• a first wiring and a second wiring,
• wherein the first transistor comprises:
• a first electrode layer;
• a first insulating layer over the first electrode layer;
• a first oxide semiconductor layer over the first insulating layer;
• a second electrode layer and a third electrode layer over the first oxide semiconductor layer;
• a second insulating layer over the second electrode layer, the third electrode layer, and the first oxide semiconductor layer, wherein the second insulating layer is in contact with the first oxide semiconductor layer;
• and
• a conductive layer over the second insulating layer, wherein the conductive layer and the first electrode layer are overlapped with each other with the first insulating layer, the first oxide semiconductor layer, and the second insulating layer interposed therebetween,
• wherein the second transistor comprises:
• a fourth electrode layer;
• the first insulating layer over the fourth electrode layer;
• a second oxide semiconductor layer over the first insulating layer;
• a fifth electrode layer and a sixth electrode layer over the second oxide semiconductor layer;
• and
• the second insulating layer over the fifth electrode layer, the sixth electrode layer, and the second oxide semiconductor layer, the second insulating layer being in contact with the second oxide semiconductor layer,
• wherein the first wiring is formed using the same material as that of the first electrode layer and the fourth electrode layer,
• wherein the second wiring comprises the same layered structure as that of the second electrode layer, the third electrode layer, the fifth electrode layer, and the sixth electrode layer, and
• wherein the pixel electrode layer is electrically connected to the second transistor.

A semiconductor device comprising:

• a substrate;
• a driver circuit portion including a first transistor over the substrate;
• a pixel portion including a second transistor and a pixel electrode layer over the substrate;
• a first alignment film over the pixel electrode layer;
• and
• a liquid crystal layer over the first alignment film,
• wherein the first transistor comprises:
• a first electrode layer;
• a first insulating layer over the first electrode layer;
• a first oxide semiconductor layer over the first insulating layer;
• a second electrode layer and a third electrode layer over the first oxide semiconductor layer;
• a second insulating layer over the second electrode layer, the third electrode layer, and the first oxide semiconductor layer, wherein the second insulating layer is in contact with the first oxide semiconductor layer;
• and
• a conductive layer over the second insulating layer, wherein the conductive layer and the first electrode layer are overlapped with each other with the first insulating layer, the first oxide semiconductor layer, and the second insulating layer interposed therebetween,
• wherein the second transistor comprises:
• a fourth electrode layer;
• the first insulating layer over the fourth electrode layer;
• a second oxide semiconductor layer over the first insulating layer;
• a fifth electrode layer and a sixth electrode layer over the second oxide semiconductor layer;
• and
• the second insulating layer over the fifth electrode layer, the sixth electrode layer, and the second oxide semiconductor layer, the second insulating layer being in contact with the second oxide semiconductor layer, and
• wherein the pixel electrode layer is electrically connected to the second transistor.

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

• forming a first gate electrode in a driver circuit portion and a second gate electrode in a pixel portion, over a substrate;
• forming a gate insulating film over the first gate electrode and the second gate electrode;
• forming a first oxide semiconductor layer and a second oxide semiconductor layer over the gate insulating film;
• performing a first heat treatment for dehydration or dehydrogenation;
• forming first source and drain electrodes over the first oxide semiconductor layer and second source and drain electrodes over the second oxide semiconductor layer;
• forming an insulating film over the first oxide semiconductor layer, the second oxide semiconductor layer, the first source and drain electrodes and the second source and drain electrodes;
• forming a conductive layer and a pixel electrode over the insulating film;
• and
• performing a second heat treatment under air atmosphere after forming the insulating film,
• wherein the first gate electrode is overlapped with the first oxide semiconductor layer and the second gate electrode is overlapped with the second oxide semiconductor layer,
• wherein the conductive layer is overlapped with the first gate electrode and the first oxide semiconductor layer, and
• wherein the pixel electrode is formed in the pixel portion.