| 摘要 |
PURPOSE:To make the concentration of an electric field at an edge hard to occur, to prevent dielectric breakdown of a gate effectively and to improve gate withstanding voltage, by rounding the edge of a polycrystalline semiconductor film constituting a gate electrode, and forming a wedge shaped oxide film, which is thicker than a gate oxide film, on the lower side of said semiconductor film. CONSTITUTION:When an p-type semiconductor layer 4 constituting a channel region is formed, p-type impurity ions are driven in an atmosphere, in which O2 is present. Thus the edge of a polycrystalline film 6 constituting a gate electrode is rounded. A wedge shaped oxide film 5g, which is far thicker than a gate insulating film, is formed between the polycrystalline silicon film 6 and the gate insulating oxide film 5a. Therefore, the concentration of an electric field at the edge of the polycrystalline silicon film 6 is suppressed, the dielectric breakdown of a gate is prevented and gate withstanding voltage is remarkably improved. Since the gate insulating layer 5a can made thin, ON resistance can be reduced, and a switching speed can be made high. |
