Importance

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Abstract

A method for fabricating an isolation region in a semiconductor substrate that produces neither a 'bird's beak' nor a 'bird's head'. A smooth substrate surface is provided, which is preferable for multi-layered wiring. The packing density of devices in a bipolar IC circuit can be increased. A sharp-edged isolation groove having a U-shaped cross-section is made by reactive ion etching. The inner surface of the isolation groove is coated by an insulating film. Then the groove is buried with polycrystalline semiconductor material. The polycrystalline material which is deposited on the surface of the substrate is etched off. At the same time the polycrystalline material in the groove is also etched to a specific depth from the surface. An insulating film is then deposited so as to again fill the groove. Then the substrate surface is polished or etched to provide a flat surface.

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First Claim