| 摘要 |
PURPOSE:To make even a thin semiconductor layer have high breakdown strength by providing a buffer semiconductor layer having a low impurity concentration at the bottom part of an element in a high breakdown strength semiconductor element where element isolation is performed by dielectric substances. CONSTITUTION:A p<+> type Si substrate 1 having an SiO2 film 2 is joined to a substrate corresponding to an n<2-> type layer 4 having an n<-> type buffer layer 10 at its base with a direct bonding technique. An element isolation groove is formed and p<+> type layers 8 as well as SiO2 film 3 are formed at the side faces of island like regions which are isolated each other and then, poly Si 5 is filled in the isolating groove. Anode p<+> type regions 7, guard ring p<-> type regions 9, and a cathode n<+> type region 6 are formed and further, electrodes 11 and 12 are formed to act as high breakdown strength diodes. The total amount of impurities in the layer 10 comes to (0.5-2.0)X10<12>/cm<2> per unit volume. When inverse voltage is impressed, depletion layers become wider in the n<2-> type layer 4 and butter layer 10. Since potential difference takes place in the transverse direction in the buffer layer, voltage is supported in the longitudinal and transverse directions. Then a thin, high breakdown strength element is formed. The embodiment of a MOS transistor and the like are demonstrated. |
