| 摘要 |
PURPOSE:To prevent lowering of impurity concentration at the surface of boron diffusion region surface and also prevent deterioration of reverse current reduction effect and deterioration after life test. CONSTITUTION:A P type region is formed as a base 12 by diffusing P type impurity to the internal surface of an N type silicon substrate 11, and an N type region is formed as an emitter 13 by diffusing an N type impurity, for example, boron to a part of internal surface. An oxide film 14 is formed by executing thermal processing in the oxygen gas ambient and then annealing is carried out by changing the ambient condition to inactive gas, for example, to the nitrogen gas ambient. A power transistor is formed by forming a base electrode 16 and emitter electrode 17. A lowered concentration at the surface of boron diffused layer is recovered by additionally executing the thermal processing under the inactive gas ambient within the same furnace at the same or higher temperature immediately after the thermal processing under the acidic ambient. |
