An optical semiconductor device includes: a photo detector section which
includes: a first semiconductor layer of a first conductivity type formed
on a surface of a semiconductor substrate of the first conductivity type,
a second semiconductor layer of a second conductivity type formed on a
surface of the first semiconductor layer, and an antireflection film
formed on a surface of the second semiconductor layer and preventing
reflection of incident light; and a circuit element section which
includes: a circuit element formed on the second semiconductor layer on
the semiconductor substrate, and a passivation film covering an uppermost
electrode layer among electrode layers constituting the circuit element
and formed out of a same material as a material of the antireflection
film.
