A Ga source gas and a nitrogen source gas are supplied to form a GaN channel layer on a semiconductor substrate. Next, a temperature is lowered while supplying at least the nitrogen source gas. Next, the Ga source gas is not supplied and an Al source gas and the nitrogen source gas are supplied. Next, the temperature is raised while not supplying the Al source gas and the Ga source gas and supplying the nitrogen source gas. Next, the Al source gas and the nitrogen source gas are supplied and at least one of the Ga source gas and an In source gas is supplied to form a AlxGayInzN barrier layer (x+y+z=1, x>0, y≥0, z≥0, y+z>0).