| 摘要 |
PURPOSE:To decrease the forward saturation voltage and thermal resistance without deteriorating the dielectric strength, by forming a recess on one surface of a semiconductor substrate before epitaxially growing a semiconductor layer on said surface. CONSTITUTION:An N<+> type semiconductor substrate 6 having a thickness of T1 is etched in the central portion of its principal face 6a to a depth of D1. When an N<-> type semiconductor layer 7 is epitaxially grown thereon to have a thickness of D2, a recess 7a is formed on its surface corresponding to the etched recess 6b in the substrate 6. The semiconductor layer 7 is sliced along the bottom of the recess 7a so as to flatten the surface of the layer 7. After that, a P-type semiconductor layer 8 is formed in a region of the epitaxial layer 7 corresponding to the etched recess 6b. In a planar diode 9 thus provide, the thickness T1 of the substrate 6 and the thickness D2 of the epitaxial layer 7 are substantially unchanged in comparison with prior arts. However, the thickness of the epitaxial layer 7 is increased by D1 in the region corresponding to the region where the P-type semiconductor layer 8 is to be formed. Therefore, the dielectric strength can be improved without increasing the forward saturation voltage or thermal resistance.
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