Disclosed herein is a composite transistor which includes a first transistor TR1 including a control electrode, a first active region, a first A extending part, and a first B extending part, and a second transistor TR2 including a control electrode, a second active region, a second A extending part, and a second B extending part. The first active region, the second active region, and the control electrode overlap one another. Both the first A extending part and the first B extending part extend from the first active region and both the second A extending part and the second B extending part extend from the second active region. The first electrode is connected to the first A extending part, the second electrode is connected to the second A extending part, and the third electrode is connected to the first B extending part and the second B extending part.