Thin film transistor and display device including thin film transistor

A thin film transistor comprising:

• a gate electrode layer;
• a first insulating layer which is provided so as to cover the gate electrode layer;
• an amorphous semiconductor layer which is provided over the first insulating layer so as to be at least partly in contact with the first insulating layer;
• a pair of impurity semiconductor layers forming a source region and a drain region, which are provided with a distance therebetween over the amorphous semiconductor layer;
• a microcrystalline semiconductor layer which is provided between the first insulating layer and the amorphous semiconductor layer in part of a channel formation region and which at least partly overlaps with the gate electrode layer and does not overlap with the pair of impurity semiconductor layers;
• and
• a second insulating layer which is provided between and in contact with the first insulating layer and the microcrystalline semiconductor layer,
• wherein the first insulating layer is a silicon nitride layer and the second insulating layer is a silicon oxynitride layer.

A thin film transistor comprising:

• a gate electrode layer;
• a first insulating layer which is provided so as to cover the gate electrode layer;
• a microcrystalline semiconductor layer which is provided over the first insulating layer and which at least partly overlaps with the gate electrode layer;
• an amorphous semiconductor layer which is provided so as to cover at least the microcrystalline semiconductor layer;
• a pair of impurity semiconductor layers forming a source region and a drain region, which are provided over the amorphous semiconductor layer and which do not overlap with the microcrystalline semiconductor layer;
• and
• a second insulating layer which is provided between and in contact with the first insulating layer and the microcrystalline semiconductor layer,
• wherein the first insulating layer is a silicon nitride layer and the second insulating layer is a silicon oxynitride layer.

A thin film transistor comprising:

• a gate electrode layer;
• a first insulating layer which is provided so as to cover the gate electrode layer;
• a pair of impurity semiconductor layers forming a source region and a drain region, which are provided with a distance therebetween and which at least partly overlap with the gate electrode layer;
• a microcrystalline semiconductor layer which is provided over the first insulating layer in part of a channel formation region and which at least partly overlaps with the gate electrode layer and one of the pair of impurity semiconductor layers and does not overlap with the other of the pair of impurity semiconductor layers;
• a second insulating layer which is provided between and in contact with the first insulating layer and the microcrystalline semiconductor layer;
• and
• an amorphous semiconductor layer which is provided over the first insulating layer so as to cover the second insulating layer and the microcrystalline semiconductor layer,
• wherein the first insulating layer is a silicon nitride layer and the second insulating layer is a silicon oxynitride layer.

A thin film transistor comprising:

• a gate electrode layer;
• a first insulating layer which is provided so as to cover the gate electrode layer;
• an amorphous semiconductor layer which is provided over the first insulating layer so as to be at least partly in contact with the first insulating layer:
• a pair of impurity semiconductor layers forming a source region and a drain region, which are provided with a distance therebetween over the amorphous semiconductor layer;
• a microcrystalline semiconductor layer which is provided between the first insulating layer and the amorphous semiconductor layer in part of a channel formation region and which at least partly overlaps with the gate electrode layer and one of the pair of impurity semiconductor layers and does not overlap with the other of the pair of impurity semiconductor layers;
• and
• a second insulating layer which is provided between and in contact with the first insulating layer and the microcrystalline semiconductor layer,
• wherein the first insulating layer is a silicon nitride layer and the second insulating layer is a silicon oxynitride layer.

A thin film transistor comprising:

• a gate electrode layer;
• a first insulating layer which is provided so as to cover the gate electrode layer;
• a microcrystalline semiconductor layer which is provided over the first insulating layer and which at least partly overlaps with the gate electrode layer;
• an amorphous semiconductor layer which is provided so as to cover at least the microcrystalline semiconductor layer;
• a pair of impurity semiconductor layers forming a source region and a drain region, which are provided over the amorphous semiconductor layer such that one of the pair of impurity semiconductor layers overlaps with the microcrystalline semiconductor layer and the other does not overlap with the microcrystalline semiconductor layer;
• and
• a second insulating layer which is provided between and in contact with the first insulating layer and the microcrystalline semiconductor layer,
• wherein the first insulating layer is a silicon nitride layer and the second insulating layer is a silicon oxynitride layer.