Semiconductor device and method for manufacturing the same

A semiconductor device, comprising:

• a first electrode;
• a second electrode, a direction from the first electrode toward the second electrode being aligned with a first direction;
• a third electrode, a position in the first direction of the third electrode being between a position in the first direction of the first electrode and a position in the first direction of the second electrode;
• a first layer including Alx1Ga1-x1N (0≤x1<1), the first layer including first to fifth partial regions, a direction from the fourth partial region toward the first electrode being aligned with a second direction crossing the first direction, a direction from the fifth partial region toward the second electrode being aligned with the second direction, a direction from the third partial region toward the third electrode being aligned with the second direction, the first partial region being between the fourth partial region and the third partial region in the first direction, the second partial region being between the third partial region and the fifth partial region in the first direction;
• a first insulating layer including a first inter-layer region and a second inter-layer region, a direction from the first partial region toward the first inter-layer region being aligned with the second direction, a direction from the second partial region toward the second inter-layer region being aligned with the second direction;
• a second layer including Alx2Ga1-x2N (0<x1<x2≤1), the second layer including a first intermediate region and a second intermediate region, the first intermediate region being provided between the first partial region and the first inter-layer region in the second direction, the second intermediate region being provided between the second partial region and the second inter-layer region in the second direction;
• and
• a third layer including Alx3Ga1-x3N (0<x1<x3≤1), the third layer including first to third nitride regions, the first inter-layer region being between the first intermediate region and the first nitride region in the second direction, the second inter-layer region being between the second intermediate region and the second nitride region in the second direction, the third nitride region being between the third partial region and the third electrode in the second direction, a crystallinity of the third nitride region being higher than a crystallinity of the first nitride region and higher than a crystallinity of the second nitride region.