BIPOLAR SEMICONDUCTOR DEVICE

摘要

PURPOSE:To reduce leak current and to improve transistor characteristics in a low current range, by providing with a thermal oxidation film which is formed more deeply and widely than the base region above the separating region. CONSTITUTION:An oxide film 7 is formed as a peripheral section of a separating region. Polysilicon 8 is buried into the central section of the separating region and constitutes the lower separating region with the oxide film 7. A depth (d) of an oxide film region 9 formed with thermal oxidation is at least deeper than the depth (d1) of the P-type base region 5 and is wider than the area of the oxide film 7 of the lower separating region, so that the region 9 can be formed so as to slightly invade into the transistor active region.