A semiconductor device includes a first semiconductor layer disposed over a substrate, a second semiconductor layer disposed over the first semiconductor layer, a gate recess disposed, through removal of a part of or all the second semiconductor layer, in a predetermined region over the first semiconductor layer, an insulating film disposed over the gate recess and the second semiconductor layer, a gate electrode disposed over the gate recess with the insulating film therebetween, and a source electrode and a drain electrode disposed over the first semiconductor layer or the second semiconductor layer, whereby a central portion of the gate recess is higher than a peripheral portion of the gate recess.