Patent ID: 7280272

Claim:
A semiconductor device comprising: a semiconductor stacking body configured so as to sandwich an active layer between a p-type semiconductor layer and an n-type semiconductor layer and having a plurality of regions along said active layer; a plurality of electrodes provided on said p-type semiconductor layer or said n-type semiconductor layer, each electrode being provided for a corresponding one of said plurality of regions; and one or more switches, each operatively connected to at least one of said plurality of electrodes configured for switching bias voltage application directions; wherein the semiconductor device is configured so that when a said switch is set to a first state, each of said plurality of regions corresponding to said at least one of the plurality of electrodes is forward biased by a voltage applied via said at least one electrode and becomes an amplification region, and, when the said switch is set to a second state, is backward biased by a voltage applied via said at least one electrode and becomes an attenuation region; a variable forward bias power source to be connected to said electrodes via said switches; a fixed backward bias power source to be connected to said electrode via said switch; and a control circuit carrying out a switching control of said one or more switches and a control of an output voltage of said variable forward bias power source to control an output power or a gain.