| 摘要 |
PURPOSE:To prevent the punch-through of boron contained in a polysilicon film which is used as a gate electrode to a substrate by forming a back gate section prior to the formation of a source. CONSTITUTION:A gate electrode composed of a gate oxide film 3 and a polysilicon film 4 is formed on a p-type epitaxial layer 2 laid on a p-type silicon substrate 1. An opening is formed on that electrode, and an n-type base layer 5 is formed with the use of the gate electrode as a mask. A window is then opened, and phosphorus ion is implanted into the window by ion-implantation. This is then subjected to forcing for thirty minutes at a temperature of 1000 deg.C to produce a back gate 8. Boron ion is then implanted with the use of a photoresist film 7 as a mask, and this is subjected to forcing at a temperature of 900 deg.C to produce a p-type source 6. Also, the polysilicon film 4 is changed to be a p-type conductivity, so that an interlayer insulating film 9 and an electrode 10 are formed. Accordingly, because of the lack of a heat treatment at a temperature of 1000 deg.C in order to produce a back gate section as it has been conventionally practiced after the formation of the p-type source, it is possible to prevent boron from diffusing into the silicon substrate.
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