METHOD OF MAKING A BIPOLAR TRANSISTOR IN A SEMICONDUCTOR SUBSTRATE

摘要

A semiconductor structure, formed within a recessed oxide isolation region, includes a semiconductor substrate of a first conductivity type within which a collector of opposite conductivity type is formed below the surface of the substrate and extending in part to the surface of the substrate for ease of contact. A first layer of doped polycrystalline silicon or polysilicon is formed on a first portion of the surface of the substrate and in electrical contact with the substrate which acts as the base of a transistor. The first polysilicon layer is oxidized to form an outer insulating layer thereover. A second doped polysilicon layer is disposed over the outer insulating layer onto a second portion of the surface of the substrate so as to be spaced from the first portion by only the thickness of the outer insulating layer on the first polysilicon layer. The dopant in the second polysilicon layer is driven into the surface of the semiconductor substrate to form an emitter therein. Means, which may include a portion of the second polysilicon layer, are provided for electrically contacting the collector to thus form a completed compact bipolar transistor which has very high performance.