Semiconductor device

A semiconductor device, comprising:

• a first electrode;
• a second electrode;
• a third electrode, a position of the third electrode in a first direction being between a position of the first electrode in the first direction and a position of the second electrode in the first direction, the first direction being from the first electrode toward the second electrode;
• a first semiconductor region including Alx1Ga1-x1N (0≤x1<1) and including a first partial region, a second partial region, a third partial region, a fourth partial region, and a fifth partial region, a second direction from the first partial region toward the first electrode crossing the first direction, a direction from the second partial region toward the second electrode being along the second direction, a direction from the third partial region toward the third electrode being along the second direction, the fourth partial region being between the first partial region and the third partial region in the first direction, the fifth partial region being between the third partial region and the second partial region in the first direction;
• a second semiconductor region including Alx2Ga1-x2N (0<x2≤1 and x1<x2) and including a sixth partial region and a seventh partial region, a direction from the fourth partial region toward the sixth partial region being along the second direction, a direction from the fifth partial region toward the seventh partial region being along the second direction;
• a third semiconductor region including Alx3Ga1-x3N (0≤x3<1 and x3<x2), the third semiconductor region including an eighth partial region, the eighth partial region being between the fifth partial region and the seventh partial region;
• a fourth semiconductor region including Alx4Ga1-x4N (0≤x4<1 and x4<x2), the fourth semiconductor region including a first portion, the first portion being between the fifth partial region and the eighth partial region, the fourth semiconductor region including a first element including at least one selected from the group consisting of Mg, Zn, and C, the first semiconductor region, the second semiconductor region, and the third semiconductor region not including the first element, or a concentration of the first element in the first semiconductor region, a concentration of the first element in the second semiconductor region, and a concentration of the first element in the third semiconductor region each being lower than a concentration of the first element in the fourth semiconductor region;
• and
• an insulating part, the insulating part including a first insulating region, a second insulating region, and a third insulating region, the first insulating region being between the third partial region and the third electrode in the second direction and between a portion of the fourth partial region and a portion of the fifth partial region in the first direction, the second insulating region being between the sixth partial region and the third electrode in the first direction, the third insulating region being between the third electrode and the first portion in the first direction, between the third electrode and the eighth partial region in the first direction, and between the third electrode and the seventh partial region in the first direction.