| 摘要 |
PURPOSE:To provide, in an ordinary SOI type substrate, a preparation method for forming a high impurity concentration area equivalent to a buried layer in an element constitution layer and at an arbitrary location inside a substrate, and to provide a transistor, which is identical in performance with a buried collector type transistor by this method. CONSTITUTION:An impurity diffusion area, which is equivalent to a buried layer, is formed by the utilization of an auxiliary layer which causes the diffusion of impurities that is faster than when it occurs in a single crystal layer. In practice, a polysilicon layer 3 is interposed between an element constitution layer 4 and an insulation layer 2, which is prepared in order to prevent contact between the constitution layer 4 and a support substrate 1. Impurities 6 at a high concentration are introduced to the bottom of the element constitution layer by the lateral diffusion via the polysilicon layer, thereby providing an arrangement equivalent to the configuration which includes a collector buried region.
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