| 摘要 |
PURPOSE:To restrain an N<+> collector diffusion layer from extending in the transversal direction, and forming a bipolar transistor region favolable to miniaturization, by connecting electrically, in the bottom of a trench, a buried N<+> layer and an N<+> type polycrystalline silicon layer buried in the trench. CONSTITUTION:The whole surface is subjected to an anisotropic etching in an atmosphere containing freon gas, and an oxide film 108 in the bottom of a trench 107 is eliminated to expose silicon. At that time, the side surface of the trench 107 is covered with the above oxide film 108. The exposed silicon substrate in the bottom of the trench is subjected to an anisotropic etching by, for example, an RIE method, in order to increase the boundary surface between an N<+> buried layer 102 and the trench. Then, polycrystalline silicon 110 containing phosphorus P is also deposited on the whole surface, and subjected to a heat treatment for about 30 min, for example, at 1000 deg.C and in N2. Thereby, at the lower part of the trench, the phosphorus diffuses into the N<+> buried layer 102 from the polycrystalline silicon, and electrical connection is completed. |
