A normally-off-type HFET includes: an undoped AlwGa1-wN layer of t1 thickness, an undoped AlxGa1-xN layer of t2 thickness and an undoped GaN channel layer of tch thickness that are sequentially stacked; a source electrode and a drain electrode separated from each other and electrically connected to the channel layer; an undoped AlyGa1-yN layer of t3 thickness formed between the source electrode and the drain electrode on the channel layer; an AlzGa1-zN layer of t4 thickness formed in a shape of a mesa on a partial area of the AlyGa1-yN layer between the source electrode and the drain electrode; and a Schottky barrier type gate electrode formed on the AlzGa1-zN layer, in which conditions of y>x>w>z, t1>t4>t3 and 2wtch/(x−w)>t2>1 nm are satisfied.