A hetero-junction semiconductor device includes: a channel layer that includes a first semiconductor; a barrier layer that is provided on the channel layer and includes a semiconductor having a band gap larger than a band gap of the first semiconductor; a source electrode and a drain electrode that are provided on the barrier layer and are ohmic contacted to the barrier layer; a p-type semiconductor layer provided on the barrier layer, the p-type semiconductor layer being provided in a region between the source electrode and the drain electrode on the barrier layer; an n-type semiconductor layer that is provided on the p-type semiconductor layer; and a gate electrode that is joined to the n-type semiconductor layer. A joint interface between the p-type semiconductor layer and the n-type semiconductor layer has a concavo-convex structure.