| 摘要 |
PURPOSE:To form a semiconductor device with a transistor having VCBO withstanding voltage larger than conventional double base structure by shaping a base region surrounding an emitter region in a deep diffusion layer having low impurity concentration. CONSTITUTION:An active base region 8a just under an emitter layer 6 is formed in a layer in which surface impurity concentration determined from transistor characteristics has impurity distribution of 2X10<18>-1X10<19>cc<-1>, and a base region 9a surrounding an emitter determining VCBO withstanding voltage is shaped in structure in which the region 9a is deeper than the active base region 8a and impurity concentration is made lower than the region 8a. Since impurity concentration in the P<+> type base region 9a surrounding the emitter in a transistor having such double base structure is lowered, the spreading width of having such double base structure is lowered, the spreading width of a space charge layer 11a in the base region 9a is increased. Accordingly, the transistor having large VCBO withstanding voltage is acquired.
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