A normally-off type field effect transistor includes: a first semiconductor layer which is made of a first hexagonal crystal with 6 mm symmetry and has a main surface including a C-axis of the first hexagonal crystal; a second semiconductor layer which is formed on the main surface of the first semiconductor layer and is made of a second hexagonal crystal with 6 mm symmetry having a band gap different from a band gap of the first hexagonal crystal; and a gate electrode, a source electrode and a drain electrode that are formed on the second semiconductor layer. Here, the film thickness of the first nitride semiconductor layer is 1.5 μm or less and the second semiconductor layer is doped with impurities at a dose of 1×1013 cm−2 or more.