A semiconductor photodetecting device including a PIN photodiode formed on an
SI-InP
substrate; a buried optical waveguide portion formed on the SI-InP substrate and
including the film thickness continuously increased toward the PIN photodiode and
an InP clad layer covering the upper surface and the side surface of the InGaAsP
core layer; and a ridge-shaped connection optical waveguide portion formed on the
SI-InP substrate between the PIN photodiode and the buried optical waveguide portion
and including the InGaAsP core layer and the InP clad layer selectively covering
only the upper surface of the InGaAsP core layer.