PURPOSE: To obtain a photodetector with a suppressed reduction in its high-frequency response characteristics due to the generation of carriers in the outside peripheral region of a P-I-N junction due to light incidence.

CONSTITUTION: A heavily doped N-type InP layer 101, a lightly doped InGaAs layer 102 and a lightly doped InP layer 103 are epitaxially grown in order on an InP substate 100. Then, a ring-shaped insulating film mask 104 is formed and a havily doped P-type layer 105 is selectively formed in the layer 103. Then, a resist mask 106 us formed in such a way as to cover an inside opening part formed in the mask 104. After that, the layers 103 and 102 are etched using the masks 104 and 106 to form a photodetecting part use mesa 107.