| 摘要 |
PURPOSE:To reduce the dispersion in element characteristics and to improve the yield rate, by performing phosphorus gettering in one surface of a semiconductor substrate, which is obtained by a direct bonding method. CONSTITUTION:On the polished mirror surface of an N<-> type Si substrate, an N<+> type layer 12 and P<+> type layer 13 are formed. The polished mirror surfaces of the N<-> type Si substrate 11 and a P<+> type Si substrate 14 are directly bonded and heat treatment is performed. Thereafter a part of the N<-> type substrate 11 is removed, and mirror surface polishing is performed. A gate electrode 17 is formed on the surface of the N<-> type substrate 11 through a gate insulating film 16 formed by the thermal oxidation. With the electrode as a mask, a P-type base region 18 is formed by B-ion implantation, and an N<+> type source region 19 is formed by As-ion implantation. The surface of the region 19 on the substrate side is covered with a CVD oxide film 20. An N<+> type layer 21 is formed on the back surface of the substrate, and phosphorus gettering is performed. The N<+> type layer 21 is removed, and a contact hole is provided in the oxide film 20. A source electrode 22 comprising an Al film, which is simultaneously contacted with the source region 19 and the P-type base region 18, is formed. A drain electrode 23 is formed on the back surface of the substrate. Thus a conduction modulation type MOSFET is completed.
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