Field effect transistor and method of manufacturing the same

A p-type nitride compound semiconductor layer is formed on a buffer formed on a substrate. An n-type contact region is formed by ion implantation under a source electrode and a drain electrode. An electric-field reducing layer made of an n-type nitride compound semiconductor is formed on the p-type nitride compound semiconductor layer. A carrier density of the electric-field reducing layer is lower than that of the n-type contact region. A first end portion of the electric-field reducing layer contacts with the n-type contact region, and a second end portion of the electric-field reducing layer overlaps with a gate electrode.