| 摘要 |
PURPOSE:To make it possible to avoid the use of an epitaxial substrate without deteriorating the characteristics of the switching transistor of a substrate plate type trench cell by a method wherein a layer containing a high-concentration impurity of the same kind as the high-concentration impurity of a substrate is formed on the interior of the sidewall of a trench excepting the vicinity of the surface of the trench. CONSTITUTION:The formation of a trench is divided into two times and after the first formation of the trench, a material which is used as a mask to a diffusing impurity, that is, an Si nitride film 34, is formed as a sidewall and after that, the formation of the trench is again executed. By forming such the trench, a trench on which the film 34 exists can be formed on the upper part of the sidewall of the trench, that is, in the vicinity of an Si substrate 11. As a result of diffusing an impurity of the same kind as the impurity of the substrate 11 in this state, a high-concentration impurity can be selectively diffused only in the trench on which the film 34 does not exist. Thereby, a switching transistor can be prevented from being exerted adverse effect on its operation at low cost without using an epitaxial substrate. |
