Patent ID: 8030728

Claim:
An optical semiconductor device comprising: a semiconductor substrate; a light receiving element formed on the semiconductor substrate; a light absorbing element formed on the semiconductor substrate and located adjacent to the light receiving element; a semiconductor element formed on the semiconductor substrate and used for signal processing; a first semiconductor layer of a first conductivity type formed over the semiconductor substrate; and a second semiconductor layer of a second conductivity type formed on the first semiconductor layer, wherein a light absorption region in the light receiving element has a different structure from a light absorption region in the light absorbing element; the light receiving element includes a part of the first semiconductor layer, a third semiconductor layer composed of a part of the second semiconductor layer and forming a PN junction with the first semiconductor layer, a first cathode contact layer of the second conductivity type formed on the third semiconductor layer and containing impurities in higher concentration than the third semiconductor layer, a fourth semiconductor layer of the first conductivity type formed on the first semiconductor layer, a first anode contact layer of the first conductivity type formed on the fourth semiconductor layer, a first cathode electrode formed on the first cathode contact layer, and a first anode electrode formed on the first anode contact layer; and the light absorbing element includes a part of the first semiconductor layer, a fifth semiconductor layer of the first conductivity type formed on the first semiconductor layer and containing impurities in higher concentration than the first semiconductor layer, a sixth semiconductor layer of the second conductivity type composed of a part of the second semiconductor layer and forming a PN junction with an upper surface of the fifth semiconductor layer, a second cathode contact layer of the second conductivity type formed on the sixth semiconductor layer and containing impurities in higher concentration than the sixth semiconductor layer, a second anode contact layer of the first conductivity type formed on the fifth semiconductor layer, a second cathode electrode formed on the second cathode contact layer, and a second anode electrode formed on the second anode contact layer.