Abstract: Disclosed is a process for producing a semiconductor device, especially, a high speed silicon gate field effect semiconductor device, by diffusing an impurity substance, such as arsenic or phosphorus, into a polycrystalline silicon layer to be converted into a silicon gate having a high electroconductivity and into portions of a single crystal silicon substrate to be converted into source and drain regions, in a sealed capsule, at an elevated temperature, under a vacuum. During the above-mentioned diffusing operation, the impurity substance can diffuse into the polycrystalline silicon layer at a higher diffusing speed than into the single crystal silicon substrate.

Abstract: A method of making a semiconductor device capable of high-speed operation is disclosed in which when the current gain-bandwidth is increased by the formation of a shallow base region. A side etching process is used to decrease the base spreading resistance and to allow ease in the formation of an emitter region of fine pattern. When the emitter region is formed by using polycrystalline silicon as a source of impurity diffusion, that area of an insulating film on a semiconductor substrate which adjoins the polycrystalline silicon is removed before the impurity diffusion so as to prevent an abnormal diffusion phenomenon.