| 摘要 |
PURPOSE: To cut down the resistance component in a drift region by a method wherein the first conductivity drain drift region in the higher impurity concentration than that equalizing voltage with the element breakdown voltage assuming the diffusion junctions are formed on the sidewall surface layer of a trench. CONSTITUTION: A drain drift region 102 e.g. in the surface impurity concentration of 1.1×10<17> cm<-3> and the diffusion depth of 0.3μm is formed on the inner surface of a trench 105 on an epitaxial substrate surface. In the off state, a depletion layer extends from the pn junctions between p base region 103/n drain drift region 2, between the n drift region 102/p impurity layer ill as well as between the p impurity layer 111/n<+> substrate 101 so as to fill up the n drain drift region 102 and the p impurity layer 111 with the depletion layer at the lower voltage than the element breakdown voltage. Thus, the positive and negative fixed charges in both regions are balanced to relieve the field for realizing a high breakdown voltage. Accordingly, the ON resistance in the n drain drift region 102 can be cut down while sustaining the high breakdown voltage.
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