| 摘要 |
PROBLEM TO BE SOLVED: To control an avalanche phenomenon in turnoff, improve the trade-off characteristic of saturation voltage-turnoff loss and RBSOA (Rutherford back scattering operation analysis), and control oscillation in turnoff in an IGBT (insulated gate bipolar transistor). SOLUTION: A formulaρ>(BV/30)<SP>4/3</SP>×0.75 is given where the resistivity of a substrate isρand a break-down voltage is BV, the conductivity of the substrate is set not to be less than 750Ωcm, preferably is set not to be less than 750Ωcm or not more than 1,250Ωcm. The IGBT having a buffer layer is constructed so that a small-carriers concentration in forward conduction is higher than an impurity concentration in the region unaffected by an electric field when a break-down voltage is applied forward. Moreover, it is constructed so that the small-carriers concentration from an well region to a collector layer in forward conduction is higher than at least the impurity concentration of part of semiconductor substrate or a buffer layer. COPYRIGHT: (C)2004,JPO
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