Patent ID: 7442972

Claim:
A semiconductor device including a photodiode region formed on the semiconductor device and isolated by element isolating regions comprising: a first semiconductor layer of a first electroconductive type; a second semiconductor layer of a second electroconductive type formed on a principal surface of said first semiconductor layer; element isolating regions of the first electroconductive type each formed extending through said second semiconductor layer to reach an outer layer portion of said first semiconductor layer in order to isolated said photodiode region; and moat regions of the second electroconductive type, each of which is formed extending through said second semiconductor layer to the outside of said photodiode region isolated by said element isolating regions and reaching the outer layer portion of said first semiconductor layer, wherein the moat regions are configured to detect an inversion layer of the second electroconductive type formed in the outer layer portion of said first semiconductor layer by applying a prescribed voltage different from a voltage applied to said second semiconductor layer in said photodiode region to at least one of said moat regions, and detecting current flowing between the at least one of said moat regions and said second semiconductor layer in said photodiode region.