Display device and electronic device having the display device, and method for manufacturing thereof

A display device including a thin film transistor, comprising:

• a gate electrode provided over a substrate;
• a gate insulating film provided over the gate electrode;
• a microcrystalline semiconductor film provided over the gate electrode with the gate insulating film interposed therebetween;
• a channel protection layer provided over the microcrystalline semiconductor film and in contact with the microcrystalline semiconductor film;
• an amorphous semiconductor film provided over the gate insulating film and on a side surface of the microcrystalline semiconductor film and the channel protection layer;
• an impurity semiconductor layer provided over the amorphous semiconductor film;
• and
• a source electrode and a drain electrode provided over and in contact with the impurity semiconductor layer,
• wherein a thickness of the amorphous semiconductor film is larger than a thickness of the microcrystalline semiconductor film,
• wherein a part of the impurity semiconductor layer and a part of the amorphous semiconductor film are exposed outside the source electrode and the drain electrode, and
• wherein one of end portions of the impurity semiconductor layer and one of end portions of the amorphous semiconductor film are aligned with each other over the gate electrode.

A display device including a thin film transistor, comprising:

• a gate electrode provided over a substrate;
• a gate insulating film provided over the gate electrode;
• a microcrystalline semiconductor film provided over the gate electrode with the gate insulating film interposed therebetween;
• a channel protection layer provided over the microcrystalline semiconductor film and in contact with the microcrystalline semiconductor film;
• an amorphous semiconductor film provided over the gate insulating film and on a side surface of the microcrystalline semiconductor film and the channel protection layer;
• an impurity semiconductor layer provided over the amorphous semiconductor film;
• a source electrode and a drain electrode provided over and in contact with the impurity semiconductor layer;
• an insulating film which is in contact with the source electrode, the drain electrode, the impurity semiconductor layer, and the amorphous semiconductor film;
• and
• a pixel electrode provided over the insulating film and connected to one of the source electrode and the drain electrode in a contact hole formed in the insulating film,
• wherein a thickness of the amorphous semiconductor film is larger than a thickness of the microcrystalline semiconductor film.

A display device including a thin film transistor, comprising:

• a gate electrode provided over a substrate;
• a gate insulating film provided over the gate electrode;
• a microcrystalline semiconductor film provided over the gate electrode with the gate insulating film interposed therebetween;
• a channel protection layer provided over the microcrystalline semiconductor film and in contact with the microcrystalline semiconductor film;
• an amorphous semiconductor film provided over the gate insulating film and on a side surface of the microcrystalline semiconductor film and the channel protection layer;
• an impurity semiconductor layer provided over the amorphous semiconductor film;
• a source electrode and a drain electrode provided over and in contact with the impurity semiconductor layer;
• an insulating film which is in contact with the source electrode, the drain electrode, the impurity semiconductor layer, and the amorphous semiconductor film;
• and
• a pixel electrode provided over the insulating film and connected to one of the source electrode and the drain electrode in a contact hole formed in the insulating film,
• wherein a thickness of the amorphous semiconductor film is larger than a thickness of the microcrystalline semiconductor film,
• wherein a part of the impurity semiconductor layer and a part of the amorphous semiconductor film are exposed outside the source electrode and the drain electrode, and
• wherein one of end portions of the impurity semiconductor layer and one of end portions of the amorphous semiconductor film are aligned with each other over the gate electrode.

A method for manufacturing a display device comprising steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film on the gate electrode;
• forming a microcrystalline semiconductor layer on the gate electrode with the gate insulating film interposed therebetween;
• forming an insulating layer on and in contact with the microcrystalline semiconductor layer;
• etching the microcrystalline semiconductor layer and the insulating layer using a mask, thereby forming a microcrystalline semiconductor island and a channel protection layer;
• forming an amorphous semiconductor film over the gate insulating film and on a side surface of the microcrystalline semiconductor island and the channel protection layer;
• forming an impurity semiconductor layer on the amorphous semiconductor film;
• forming a conductive layer on the impurity semiconductor layer;
• and
• etching the conductive layer, the impurity semiconductor layer, and the amorphous semiconductor film, thereby forming source and drain electrodes.

A method for manufacturing a display device comprising steps of:

• forming a gate electrode over a substrate;
• forming a gate insulating film on the gate electrode;
• forming a microcrystalline semiconductor layer on the gate electrode with the gate insulating film interposed therebetween;
• forming an insulating layer on and in contact with the microcrystalline semiconductor layer;
• etching the microcrystalline semiconductor layer and the insulating layer using a mask, thereby forming a microcrystalline semiconductor island and a channel protection layer;
• forming an amorphous semiconductor film over the gate insulating film and on a side surface of the microcrystalline semiconductor island and the channel protection layer;
• forming an impurity semiconductor layer on the amorphous semiconductor film;
• forming a conductive layer on the impurity semiconductor layer;
• etching the conductive layer, the impurity semiconductor layer, and the amorphous semiconductor film, thereby forming source and drain electrodes;
• forming an insulating film in contact with the source and drain electrodes, the impurity semiconductor layer, and the amorphous semiconductor film;
• and
• forming a pixel electrode over the insulating film, the pixel electrode connected to one of the source and drain electrodes in a contact hole formed in the insulating film.