| 摘要 |
A vertical MOSFET of the present invention comprises a semiconductor wafer having a groove selectively etching in the semiconductor wafer to have substantially vertical side walls. The groove is oxidized using local oxidation of silicon (LOCOS) at 1100 DEG C. or greater to form a LOCOS film on the semiconductor wafer in the groove so that a whole side surface of said semiconductor wafer exposed by the groove is substantially vertical and essentially flat. The LOCOS film in the groove is removed and a thermal insulating film on the semiconductor wafer in the groove. Then a gate electrode made of a conductive film is formed on the thermal insulating film. An interlayer insulating film is formed on the gate electrode and a source electrode is formed in ohmic contact with a source region and a base region. A drain electrode is connected to the opposite side of the semiconductor wafer. As a result, the vertical MOSFET of the present invention has improved on-state resistance, reduced parasitic capacitance and higher breakdown voltage.
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