Semiconductor device and method for manufacturing same

The invention provides a semiconductor device and a method for manufacturing same. The semiconductor device is provided with: a buffer layer (102), which is provided on a substrate (101), and is composed of a III-V nitride semiconductor; a first semiconductor layer (103), which is provided on the buffer layer (102), and is composed of a III-V nitride semiconductor; a second semiconductor layer (104), which is provided on the first semiconductor layer (103), and is composed of a III-V nitride semiconductor; a rear-surface electrode (111), which is provided on the rear surface of the substrate (101), and is connected to the ground; a source electrode (132) and a drain electrode (134), which are provided on the second semiconductor layer (104) by being spaced apart from each other; a gate electrode (136), which is provided on the second semiconductor layer (104); and a plug (109), which penetrates the second semiconductor layer (104), the first semiconductor layer (103) and the buffer layer (102), reaches at least the substrate (101), and electrically connects the source electrode (132) and the rear-surface electrode (111) to each other.