Thin-film semiconductor device, lateral bipolar thin-film transistor, hybrid thin-film transistor, MOS thin-film transistor, and method of fabricating thin-film transistor

1. A thin-film semiconductor device comprising:

a substrate formed of glass or plastic;

a semiconductor film formed on one side of the substrate, the semiconductor film including a single-crystal grain which is crystallized in a lateral direction, wherein the semiconductor film has a T shaped pattern formed by a lateral portion and a width portion extended from the lateral portion;

an MOS transistor including a source region, a channel region and a drain region, which are formed in the single-crystal grain, and including a gate electrode formed on the channel region via an insulation film, carriers in the source, channel and drain regions being moved in the lateral direction; and

a lateral bipolar transistor including an emitter, a base and a collector, the emitter being formed by the source region, the base being formed by the channel region, and the collector being formed by at least one part of the drain region, wherein the MOS transistor and the lateral bipolar transistor are formed in the lateral portion, and a base contact portion is formed in the width portion, one side of the base contact portion being connected to one end of the base and having an impurity concentration higher than that of the collector.

2. The thin-film semiconductor device according to claim 1 , wherein the lateral bipolar transistor includes a collector contact portion which is formed in the single-crystal grain, and has an impurity concentration higher than that of the collector, and the drain region includes the collector contact portion and the collector.

3. The thin-film semiconductor device according to claim 1 , wherein the base has a width of at least 5 μm, the width being normal to the lateral direction.