Nitride semiconductor stacked structure and method for manufacturing same and nitride semiconductor device

A nitride semiconductor stacked structure having a first surface on which a semiconductor including InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, x+y≦1) can be stacked, the structure comprising:

• a substrate having a step portion, the step portion including an upper surface, a lower surface, and a side surface between the upper surface and the lower surface;
• a first buffer layer including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦1) and covering the lower surface and the side surface;
• a first crystal layer provided on the first buffer layer, including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦0.05), and having an upper surface provided above the upper surface of the substrate;
• a selective growth mask layer provided on the upper surface of the substrate;
• a second buffer layer including AlwGa1-wN (0.6≦w≦1) and continuously covering the upper surface of the first crystal layer and an upper surface of the selective growth mask layer;
• and
• a second crystal layer covering the second buffer layer, including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦0.05), and having the first surface.

A nitride semiconductor device comprising:

• a nitride semiconductor stacked structure including:
• a substrate having a step portion, the step portion including an upper surface, a lower surface, and a side surface between the upper surface and the lower surface;
• a first buffer layer including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦1) and covering the lower surface and the side surface;
• a first crystal layer provided on the first buffer layer, including InsAltGa1-s-tN (0≦s≦0.05, 1≦t≦0.05), and having an upper surface provided above the upper surface of the substrate;
• a second buffer layer including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦1) and continuously covering the upper surface of the first crystal layer and the upper surface of the substrate;
• and
• a second crystal layer covering the second buffer layer and including InsAltGa1-s-tN (0≦s≦0.05, 0≦t≦0.05);
• and
• a semiconductor stacked on the second crystal layer and including InxAlyGa1-x-yN (0≦x≦1, 0≦y≦1, x+y≦1).