Semi-insulating polycrystalline-silicon (SIPOS) films have been used as a replacement of a silicon dioxide passivation layer of planar devices. The SIPOS films are chemically vapordeposited polycrystalline-silicon doped with oxygen or nitrogen atoms. The passivation properties of oxygen-doped SIPOS films have been examined as a function of oxygen concentration. The npn and pnp transistors rated at 800 V and 2500 V have been produced by the SIPOS process in planar-like structures with field-limiting rings. The leakage currents of 800 V pnp transistors did not increase even after the chips were exposed to water vapor at 100°C and to sodium contamination at 200°C. Thus, the SIPOS transistors can be packaged in low-cost molded epoxy as well as metal cans. Furthermore, 10 kV SIPOS transistors with multiple rings have been fabricated and their operation has been found to be stable.

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