MOS TRANSISTOR AND MANUFACTURE THEREOF

• Main Author: MOMOTOMI MASAKI
• Format: Patent
• Language: English
• Published: 03.06.1988
• Subjects: BASIC ELECTRIC ELEMENTS; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR; ELECTRICITY; SEMICONDUCTOR DEVICES

PURPOSE:To obtain a MOS transistor having high current supply capacity and high breakdown strength by forming a gate electrode to an inverted projecting shape and making the thickness of a gate insulating film at the side end section of a drain region in a gate region thicker than that of the central section of the gate region. CONSTITUTION:A gate electrode 3 is shaped to a p-type Si substrate 1 through a gate oxide film 2. The gate electrode 3 is constituted of the laminated films of a first layer polycrystalline silicon film 31, to which phosphorus is doped in high concentration, and a second layer polycrystalline silicon film 32 to which phosphorus is doped in concentration lower than the film 31. The gate electrode 3 is formed to an inverted projecting shape in such a manner that it is thermally oxidized after the laminated films are shaped to a pattern and the side surface of the first layer polycrystalline silicon film 31 is oxidized in the lateral direction in size deeper than the side surface of the second layer polycrystalline silicon 32. That is, the gate oxide film 2 is thickened substantially at end sections. Accordingly, high surface breakdown strength can be acquired.