The present invention provides a semiconductor device in which a V-groove for holding an optical fiber and an alignment groove for adjusting the distance between the optical fiber and an optical element chip are formed in an optical fiber packaging region on the upper face of a semiconductor substrate, and an optical element chip is packaged in an optical element packaging region on the upper face of the semiconductor substrate so that its optical axis matches the direction in which the V-groove extends. A semiconductor integrated circuit is formed on the lower face of the semiconductor substrate. Through holes are provided in the optical element packaging region of the semiconductor substrate, passing from its upper face to its lower face, and the optical element chip and the semiconductor integrated circuit are connected via the through holes.