| 摘要 |
PURPOSE:To prevent fluctuation in threshold voltage and the breakdown of a gate insulation film, by forming, the gate insulation film so that a gate electrode is located only on a low density region, in a constitution, wherein source and drain regions are formed by neighboring two diffusions at low concentration and high concentration. CONSTITUTION:A gate electrode 5 is provided at a position in the following way: the position is not located on a high concentration region 6 of double diffursed source and drain regions, but located only on a low concentration region 7; and a depletion region 8, which is formed in a P-N junction when a drain voltage is applied, expands outward from the part directly below the gate electrode 5. Owing to the double diffusions, the expanse of the depletion layer 8 between substrate parts becomes large, and the withstand voltage is improved. Since the gate electrode is provided only to the intermediate part of the depletion layer 8, the applying way of an electric field in such that hot carriers are hard to be inputted in a gate insulating film 3. Therefore, the fluctuation in threshold voltage can be eliminated, and deterioration in gate breakdown withstanding voltage can be prevented. |
