a nitride semiconductor device , which includes a iii - v group nitride semiconductor layer being composed of a iii group element consisting of at least one of a group containing of gallium , aluminum , boron and indium and v group element consisting of at least nitrogen among a group consisting of nitrogen , phosphorus and arsenic , including a first nitride semiconductor layer including the iii - v group nitride semiconductor layer being deposited on a substrate , a second nitride semiconductor layer including the iii - v group nitride semiconductor layer being deposited on the first nitride semiconductor and not containing aluminum and a control electrode making schottky contact with the second nitride semiconductor layer wherein the second nitride semiconductor layer includes a film whose film forming temperature is lower than the first nitride semiconductor layer .