Nitride semiconductor device comprising layered structure of active region and method for manufacturing the same

A nitride semiconductor device comprising:

• a GaN layer;
• an AlGaN layer formed on the GaN layer;
• a plurality of drain contacts and a plurality of source contacts formed over the AlGaN layer, the plurality of drain contacts and the plurality of source contacts arranged alternately in a first direction;
• a concave portion formed at an edge portion of the nitride semiconductor device in a cross-section viewed from a second direction orthogonal to the first direction in plan view, a bottom portion of the concave portion formed by the GaN layer;
• an active region that has a layered structure including the GaN layer and the AlGaN layer;
• an inactive region that is formed at the layered structure around the active region and that is the concave portion having the bottom portion that reaches the GaN layer;
• a gate layer that is formed on the AlGaN layer in the active region;
• a gate electrode formed on the gate layer;
• a first insulating film that covers the gate electrode and that is formed on the AlGaN layer in the active region;
• and
• a second insulating film that covers the first insulating film and that is formed on the inactive region, wherein
• the second insulating film is a multi-layer film,
• the first insulating film is a nitride film,
• the second insulating film includes a lower layer and an upper layer, and
• the lower layer is thinner than the upper layer.