Germanium (Ge) contamination to a semiconductor manufacturing apparatus is suppressed. Germanium is a dissimilar material in a silicon semiconductor process. A semiconductor device is provided with a Ge photodiode including an n-type germanium layer, and a plug capacitively coupled to the n-type germanium layer. In other words, the n-type germanium layer of the Ge photodiode and the plug are not in direct contact with each other but are capacitively coupled to each other.