| 摘要 |
PURPOSE:To control concentration distribution of an epitaxial layer uniformly, by forming an epitaxial layer of a reverse conductive type on a semiconductor substrate of a conductive type in such a manner that impurity concentration in the substrate becomes higher toward further distance from the interface with the epitaxial layer. CONSTITUTION:A photo-resist membrane is formed on an oxide membrane 4 on a P type low-density Si substrate 3. By thermally dispersing impurity of the same conductive type on this substrate 3, concentration gradient is given in the substrate 3. After removing the photoresist membrane, an N type low-density epitaxial layer 5 is formed thereon by gaseous phase growth. As for impurity concentration distribution of the substrate, the P type impurity concentration gets higher toward further distance from the epitaxial layer 5 providing a low resistance and a good ohmic contact. As the concentration is low on the epitaxial layer side, it is not doped automatically at the time of gaseous phase growth, and therefore, uniform concentration can be maintained. It is possible, by doing so, to form a semiconductor element of good electrical characteristics. |
