| 摘要 |
PURPOSE:To obtain a high withstand voltage MOSFET in good saturation characteristic by a method wherein when a high withstand voltage layer is formed on a source and the upper part of a drain region located on both sides of a gate electrode, the concentration of impurities on the drain side is kept higher than that of the source side. CONSTITUTION:A gate SiO2 film 2 is attached to a P type Si substrate 1, a polycrystalline Si gate electrode 3 given a conductive property by containing impurities therein is formed at a prescribed position on the film 2, and with the gate electrode 3 as a mask, an N<-> type high withstand voltage layer 4 is formed by driving ions in the surface of the substrate 1. Then, an N<+> type source region 8 and a drain region 9 are formed by driving ions through the layer 4. An N<+> type layer 6 is formed between the layer 4 and the region 9 by injection ions at this time in advance to the layer 4 adjacent to the region 9. Thus, the saturation characteristic is improved while changing partially the concentration of impurities of the high withstand voltage layer 4 and simplifying the process. |
