The invention is directed to improve characteristics of an HBT (Hetero-junction Bipolar Transistor). An HBT has a collector layer, a base layer, and an emitter layer formed in order on a main surface of a substrate made of a compound semiconductor and a collector electrode, a base electrode, and an emitter electrode electrically connected to the collector layer, the base layer, and the emitter layer, respectively, and further has an emitter contact layer formed between the emitter electrode and the emitter layer. The plane shape of the emitter contact layer and the emitter electrode is an almost annular shape surrounding the base electrode in a plane parallel with the main surface of the substrate, and the lower limit of the emitter contact layer is 1.2 μm or larger.