| 摘要 |
PURPOSE:To improve the noise characteristic of a high frequency transistor element by forming a polysilicon layer insulating film on a base region, then overetching the polysilicon, implanting impurity ions on the base region with the remaining insulating film as a mask, then reforming the insulating film, and then vertically etching it. CONSTITUTION:A P type base layer 2 is formed on an N type silicon substrate 1. Then, a polysilicon layer 7 which contains an N type impurity and a silicon oxide film 8 or a silicon nitride film are formed. Then, a photoresist 9 is allowed to remain, with the photoresist 9 as a mask the film 8 is corroded and removed. Then, with the film 8 as a mask the layer 7 is overetched, and the film 8 is allowed to remain as an overhang state. Thereafter, with the photoresist 9 and the film 8 as masks P type impurity such as boron ions are implanted. Then, the photoresist and the silicon oxide film are removed, and an insulating film is formed on the surface of the silicon substrate. Thereafter, a heat treatment is performed. Then, the semiconductor substrate is vertically dry etched by a reactive sputtering unit. |
