Semiconductor device and method for manufacturing the same

A semiconductor device, comprising:

• a first electrode;
• a second electrode, a direction from the second electrode toward the first 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, a direction from the fifth partial region toward the second electrode, and a direction from the third partial region toward the third electrode being aligned with a second direction crossing the first 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 second layer including Alx2Ga1-x2N (0<x2≤1), the second layer including a first semiconductor region and a second semiconductor region, a direction from the first partial region toward the first semiconductor region and a direction from the second partial region toward the second semiconductor region being aligned with the second direction;
• a third layer including Alx3Ga1-x3N (0<x3≤1), the third layer including first to third intermediate regions, the first intermediate region being provided between the first partial region and the first semiconductor region in the second direction, the second intermediate region being provided between the second partial region and the second semiconductor region in the second direction, the third intermediate region being provided between the third partial region and the third electrode in the second direction;
• a fourth layer including Alx4Ga1-x4N (0≤x4<1, x4<x1, x4<x2, and x4<x3), the fourth layer being provided between the first partial region and the first intermediate region, between the second partial region and the second intermediate region, and between the third partial region and the third intermediate region in the second direction;
• and
• an insulating portion including a first insulating region provided between the third layer and the third electrode in the second direction,
• a first concentration of the first element at a first position inside a region including the first intermediate region and the first semiconductor region being higher than a third concentration of the first element at a third position inside the third intermediate region,
• a direction from the third position toward the first position being aligned with the first direction,
• the first element including at least one selected from the group consisting of silicon, oxygen, carbon, and magnesium.