This invention prevents an end portion of the LOCOS region having a large number of defects of an MOS sensor from depletion and thereby reduces the leak current that occurs in the defects in the end portion of the LOCOS region. An n-type layer region is formed in a surface area of a p-type substrate for constituting a photodiode with the p-type layer. A LOCOS region is formed on a p+-type layer in a surface area of the silicon substrate as device separation region by oxidizing part of the silicon substrate. The n-type layer region and the LOCOS region are separated from each other by a predetermined distance. A contact region is formed and separated from the n-type layer region by a distance equal to the size of the gate electrode of the read-out transistor of the MOS sensor. A wiring layer is connected to the contact region. Then, a planarizing layer is formed to cover the n-type layer region, the LOCOS region, the gate electrode and the wiring layer.