| 摘要 |
A vertical type MOSFET, in which an N type high resistance drift layer (102) is formed on an N type substrate (101) and P type base layers (103) are formed in designated regions of the surface of the high resistance drift layer and N type source layers (104) are formed in the base layers and gate electrodes (105) are formed on specified regions of the surface of the high resistance drift layer, a trench type back gate section (109) is formed in a trench (110) positioned at a region between the gate electrodes, by filling an insulation material (111) in the trench. Also, P type impurity layers (112) are formed in the high resistance drift layer at the region directly under the trench type back gate section. The P type impurity layers are formed by implanting ions from the bottom of the trench, after the trench is formed. After this, the trench is filled with an insulation material. With this, by securing the breakdown voltage of about 150V (middle class) by the provision of the impurity layers, the concentration of the impurity in the high resistance drift layer is made to be higher, the drift resistance is lowered.
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