PURPOSE: To obtain a MOS type semiconductor integrated circuit whose resistance to radiation is excellent, by arranging an electrode in a field oxide film for element isolation, and connecting the electrode to a ground lead.

CONSTITUTION: An electrode 8 is arranged in a field oxide film 3 for element isolation, and the electrode is connected to a ground lead. For example, after the field oxide film 0.5W1μm thick is formed by a long time oxidation process, a trench for a shielding electrode is formed in the field oxide film 3 by dry etching, and polysilicon is buried in the trench. After that, the polysilicon is oxidized, and the shielding electrode 8 is formed in the field oxide film 3. Thereby, a thin oxide film is obtained in a deep position from the substrate surface, and the leak current at the time of radiation exposure can be reduced. Further, the leak current due to the decrease of threshold voltage cauded by radiation exposure can be prevented from generating, by connecting the shielding electrode 8 to the ground lead.