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 semiconductor layer including Alx1Ga1-x1N (0<x1≤1), the first semiconductor 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 nitride layer including silicon and nitrogen, a ratio Si/N of a concentration of silicon (Si) in the nitride layer to a concentration of nitrogen (N) in the nitride layer being not less than 0.68 and not more than 0.72, the nitride layer including a first nitride region and a second nitride region;
• a second semiconductor layer including Alx2Ga1-x2N (0<x2≤1), the second semiconductor layer including a first semiconductor region and a second semiconductor region, the first semiconductor region being provided between the first partial region and the first nitride region in the second direction and contacting the first nitride region, the second semiconductor region being provided between the second partial region and the second nitride region in the second direction and contacting the second nitride region;
• an oxide layer including silicon and oxygen, a concentration of nitrogen in the oxide layer being lower than a concentration of nitrogen in the nitride layer, the oxide layer including first to third oxide regions, at least a portion of the first nitride region being provided between the first oxide region and the second semiconductor region, at least a portion of the second nitride region being provided between the second oxide region and the second semiconductor region, the third oxide region being provided between the third partial region and the third electrode and contacting the third partial region and the third electrode.