| 摘要 |
PURPOSE:To prevent mask alignment from being displaced and to prevent an oxide film from being side-etched, by forming a polysilicon coating on a hole having a diffusion layer formed therein. CONSTITUTION:A base region 3 is formed on the collector region 2 of the silicon wafer 1 and an oxide film 4 is adhered thereon. Next, three holes 9 are opened at regular intervals, a thinner oxide film 4 is formed, a photo resist 10 is coated thereon and is then photo-etched on the central hole 9 to open a little wide, and the oxide film lying on this section is etched. Next, the photo resist 10 is removed, a polysilicon coating 11 is formed, a photo resist 10 is again adhered thereon, photo etching opens the photo resist 10 only on the central hole 9 a little wide, impurities are ion-implanted, and then thermal diffusion forms an emitter region 6. Thereafter, with being left only on the central hole 9, the other polysilicon coating 11 is removed. Using the coating 11 as a mask, the oxide film 4 is etched and electrodes 12 are formed on the respective holes 9 to finish a high frequency transistor. |
