| 摘要 |
PROBLEM TO BE SOLVED: To prevent the destruction or deterioration of a gate insulating film by the concentration of an electric field and to manufacture the UMOS semiconductor device of high breakdown voltage by making the depth of a trench to be shallower then a second conductive base area. SOLUTION: In a SiC vertical MOSFET element, the depth of a trench 24 is formed to be shallower than a p-base area 22. When positive voltage is applied to a gate electrode layer 26, an accumulation layer is generated an n-side wall area 20b, a part between a drain electrode 28 and a source electrode 27 is conducted, current is made to flow and it is interrupted when the voltage of the gate electrode 26 is removed. In trench MOSFET, the pn-junction exists in the p-base area 22 in a part deeper than the trench 24. A part where an electric field is concentrated becomes a pn-junction part. Thus, the electric field is prevented from being concentrated on the corner part of the trench 24, tress to a gate insulating film 25 is less and high breakdown voltage becomes possible.
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