| 主权项 |
1. A fabrication method for a semiconductor device, comprising the steps of:
preparing a substrate having a semiconductor layer provided on a principal surface; forming a trench in the semiconductor layer; forming a gate insulating film on a side of the trench, a bottom of the trench, and a periphery of the trench; and forming a conductive film on the gate insulating film to fill the trench and extend on the periphery of the trench, wherein the step of forming a gate insulating film includes a step of forming a first insulating film on the side of the trench and a step of forming a second insulating film on the bottom of the trench and the periphery of the trench using a high-density plasma chemical vapor deposition method, the thickness of portions of the gate insulating film formed on the bottom of the trench and the periphery of the trench being made larger than a thickness of a portion of the gate insulating film formed on the side of the trench, in the step of forming a conductive film, the conductive film is formed to be in contact with a portion of the first insulating film formed on the side of the trench, in the step of preparing a substrate, the semiconductor layer is formed to include a drift region of a first conductivity type and a body region of a second conductivity type provided on the drift region, in the step of forming a trench, the trench is formed so that the bottom of the trench is located below an interface between the drift region and the body region and above a bottom of the drift region, and in the step of forming a gate insulating film, the gate insulating film is formed so that a top surface of the portion thereof formed on the bottom of the trench is located below the interface between the drift region and the body region. |
