Thin film transistor structure having increased on-current

A thin film transistor structure comprising:

• a base plate;
• a control electrode layer formed on a part of said base plate;
• an insulating layer formed on said control electrode layer and on said base plate;
• an active layer of a semiconductor material formed on a part of said insulating layer which is on said control electrode layer;
• first and second main electrode layers formed above said active layer in a spaced relation to define, in cooperation with said control electrode layer, a channel in said active layer between said first and second main electrode layers;
• and
• first and second heavily doped semiconductor layers provided between said active layer and said first main electrode layer and between said active layer and said second main electrode layer, respectively, in which
• said active layer having a first peripheral edge portion generally perpendicular to the direction of said channel and a second peripheral edge portion generally not perpendicular to the direction of said channel, and
• at least one of said first and second main electrode layers and the underlying heavily doped semiconductor layer extending over said first peripheral edge portion of said active layer onto said insulating layer such that at least a part of said first peripheral edge portion of said active layer has its side face directly covered with said heavily doped layer and that a part of said one main electrode layer overlaps said control electrode only with said heavily doped layer and insulating layer lying therebetween, the length of said overlapping part of said one main electrode layer as measured in the direction of said channel being not smaller than the thickness of said active layer.

A thin film transistor structure comprising:

• a base plate;
• a control electrode layer formed on a part of said base plate;
• an insulating layer formed on said control electrode layer and on said base plate;
• an active layer of a semiconductor material formed at least on a part of said insulating layer which is on said control electrode layer;
• and
• first and second main electrode layers in an overlap relation to that surface of said active layer which is not on said insulating layer, said first and second main electrode layers being spaced from each other to define, in cooperation with said control electrode layer, a channel in said active layer between said first and second main electrode layer, in which
• said active layer has a first peripheral edge portion generally perpendicular to the direction of said channel and a second peripheral edge portion generally not perpendicular to the direction of said channel, and
• at least one of said first and second main electrode layers extends over said second peripheral edge portion of said active layer onto said insulating layer such that at least a part of said second peripheral edge portion of said active layer has its side face directly covered with said at least one main electrode layer.

A thin film transistor structure comprising:

• a base plate;
• a control electrode layer formed on a part of said base plate;
• an insulating layer formed on said control electrode layer and on said base plate;
• an active layer of a semiconductor material formed on a part of said insulating layer which is on said control electrode layer;
• first and second main electrode layers formed above said active layer in a spaced relation to define, in cooperation with said control electrode layer, a channel in said active layer between said first and second main electrode layers;
• and
• first and second heavily doped layers provided between said active layer and said first main electrode layer and between said active layer and said second main electrode layer, respectively, in which
• said active layer has a first peripheral edge portion generally perpendicular to the direction of said channel and a second peripheral edge portion generally not perpendicular to the direction of said channel, and
• at least one of said first and second main electrode layers and the underlying heavily doped layer extends over said second peripheral edge portion of said active layer onto said insulating layer such that at least a part of said second peripheral edge portion of said active layer has its side face directly covered with said heavily doped layer.