A method for fabricating a semiconductor device according to the present invention includes the steps of: growing a p-type gallium nitride-based compound semiconductor layer by performing a metalorganic chemical vapor deposition process in a heated atmosphere so that the crystal-growing plane of the semiconductor layer is an m plane (Step S13); and cooling the p-type gallium nitride-based compound semiconductor layer (Step S14) after the step of growing has been carried out. The step of growing includes supplying hydrogen gas to a reaction chamber in which the p-type gallium nitride-based compound semiconductor layer is grown. The step of cooling includes cooling the p-type gallium nitride-based compound semiconductor layer with the supply of the hydrogen gas to the reaction chamber cut off.