| 摘要 |
PURPOSE:To decrease an epitaxial layer of a current passage in width and improve a bipolar transistor in a current gain by a method wherein a phosphorus buried layer whose area is smaller than the cross-sectional area of the current passage is provided transversing the current passage of a high breakdown strength element. CONSTITUTION:A phosphorus buried layer 10 is provided just under a base region 3. The area of the buried layer 10 is smaller than that of the base region 3. Phosphorus contained in the buried layer 10 is larger than antimonium contained in a substrate 1 in a diffusion coefficient, so that phosphorus is diffused into an epitaxial layer 2 which is smaller than the substrate 1 in concentration through a heat treatment performed for the formation of the base region 3 and an emitter region 4 and the low concentrated epitaxial layer 2 under the base region 3 is made to be smaller in substantial width. By these processes, a drop in a current gain is nearly prevented, a collector resistance decreases, and the Vce is made to decrease also. As regards a switching property, a storage period can be decreased. |
