| 摘要 |
PROBLEM TO BE SOLVED: To provide an IGBT which optimum sets the on-loss, switching speed and serge withstanding power being IGBT characteristics when the withstand voltage of a pn parasitic diode is high and low. SOLUTION: A first buffer layer 2a near a silicon substrate 1 and second buffer layer 2b on other portions have a high and low concentrations of an n-type impurity, respectively, resulting in some concentration difference. This raises the concentration of the n-type impurity near the substrate 1, and hence an IGBT is obtained with a high switching speed and a sufficient L-load surge withstand power. The concentration of the n-type impurity is not high in all the buffer layers, this preventing the on-voltage being excessively high with leaving the on-loss low. COPYRIGHT: (C)2006,JPO&NCIPI
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