| 摘要 |
According to an embodiment, in a nitride-based FET, a protrusion portion is formed at an upper portion of an undoped GaN layer by second recess etching. On the protrusion portion, an undoped AlGaN layer is provided which is formed by first recess etching the upper portion of the undoped AlGaN layer. A multilayer portion is composed of the protrusion portion of the undoped GaN layer, the undoped AlGaN layer, and an insulating film. A trench portion is formed by recess etching the insulating film, the undoped AlGaN layer and a surface of the undoped GaN layer. A gate insulating film is formed on the multilayer portion and the trench portion. A gate electrode is formed on the gate insulating film so as to cover the trench portion. A film thickness of the insulting film is set larger than that of the gate insulating film.
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