Compound semiconductor device and manufacturing method of the same
An electrode ( 109 ) insulated from a compound semiconductor layer ( 102 ) and being in contact with an electrode ( 101 ) and a compound semiconductor layer ( 103 ) is provided. A lattice constant of the compound semiconductor layer ( 103 ) is smaller than both of a lattice constant of the compound semiconductor layer ( 102 ) and a lattice constant of a compound semiconductor layer ( 104 ), and a lattice constant of a compound semiconductor layer ( 107 ) is smaller than both of the lattice constants of the compound semiconductor layer ( 102 ) and the lattice constants of the compound semiconductor layer ( 104 ). A conduction band energy of the compound semiconductor layer ( 103 ) is higher than a conduction band energy of the compound semiconductor layer ( 104 ).
1. A manufacturing method of a compound semiconductor device, comprising:
forming a stack in which a first compound semiconductor layer, a second compound semiconductor layer and a third compound semiconductor layer are stacked in this sequence;
forming an opening in the stack;
forming a fourth compound semiconductor layer in the opening, the fourth compound semiconductor layer being in contact with side surfaces of the first compound semiconductor layer, the second compound semiconductor layer and the third compound semiconductor layer, and the side surfaces facing to the opening;
forming a gate electrode that controls an electric potential of an interface between the second compound semiconductor layer and the fourth compound semiconductor layer;
forming a second electrode over the third compound semiconductor layer;
forming a first electrode beneath the first compound semiconductor layer; and
forming a third electrode insulated from the first compound semiconductor layer, the third electrode being in contact with the first electrode and the second compound semiconductor layer, wherein
a lattice constant of the second compound semiconductor layer is smaller than both of a lattice constant of the first compound semiconductor layer and a lattice constant of the third compound semiconductor layer,
a lattice constant of the fourth compound semiconductor layer is smaller than both of the lattice constant of the first compound semiconductor layer and the lattice constant of the third compound semiconductor layer, and
a conduction band energy of the second compound semiconductor layer is higher than a conduction band energy of the third compound semiconductor layer.
2. The manufacturing method of a compound semiconductor device according to claim 1 , wherein the third electrode is formed apart from two-dimensional electron gas generated resulting from a difference of the lattice constants between the first compound semiconductor layer and the fourth compound semiconductor layer and two-dimensional electron gas generated resulting from a difference of the lattice constants between the third compound semiconductor layer and the fourth compound semiconductor layer.
3. The manufacturing method of a compound semiconductor device according to claim 1 , wherein the lattice constant of the second compound semiconductor layer is equal to or less than the lattice constant of the fourth compound semiconductor layer.
4. The manufacturing method of a compound semiconductor device according to claim 1 , further comprising forming a gate insulating film that insulates the gate electrode and the fourth compound semiconductor layer from each other.
5. The manufacturing method of a compound semiconductor device according to claim 4 , wherein the forming the gate insulating film comprises forming an insulating film thicker than the gate insulating film, the insulating film insulates the gate electrode and the first electrode from each other.
6. The manufacturing method of a compound semiconductor device according to claim 1 , wherein the first electrode and the third electrode are integrally formed.
7. The manufacturing method of a compound semiconductor device according to claim 1 , wherein
each of the first compound semiconductor layer, the second compound semiconductor layer and the third compound semiconductor layer contains Ga and N, and
each of front surfaces of the first compound semiconductor layer, the second compound semiconductor layer and the third compound semiconductor layer is perpendicular to an a-axis direction.
8. The manufacturing method of a compound semiconductor device according to claim 1 , wherein
each of the first compound semiconductor layer, the second compound semiconductor layer and the third compound semiconductor layer contains Ga and N, and
a plane orientation of each of the side surfaces is (0001).