Manufacturing method of semiconductor device and semiconductor device

A semiconductor device comprising:

• a first nitride semiconductor layer formed above a substrate;
• a second nitride semiconductor layer being formed over the first nitride semiconductor layer and having an electron affinity smaller than the first nitride semiconductor layer;
• a trench penetrating the second nitride semiconductor layer and reaching the middle of the first nitride semiconductor layer;
• a gate electrode being formed over the second nitride semiconductor layer with a gate insulation film interposed between the gate electrode and the second nitride semiconductor layer and the gate electrode extending in a first direction;
• a first electrode coupled to the second nitride semiconductor layer on one side of the gate electrode;
• and
• a second electrode coupled to the second nitride semiconductor layer on the other side of the gate electrode,
• wherein the first electrode is formed above the gate electrode with a first insulation film interposed between the first electrode and the gate electrode, the first electrode extends beyond the gate electrode in a second direction intersecting with the first direction, and the first electrode has a hole,
• wherein the length of the hole in the first direction is larger than the length of the trench in the first direction, and
• wherein the width of the hole in the second direction is larger than the width of the trench in the second direction and smaller than the width of the gate electrode in the second direction.