Semiconductor device, method for manufacturing semiconductor device, and electronic device

A method for manufacturing a semiconductor device, the method comprising:

• forming a barrier layer that includes a second nitride semiconductor on a first surface side of a channel layer that includes a first nitride semiconductor;
• forming a polarization layer that includes a third nitride semiconductor that contains Al, on a second surface side opposite to the channel layer side, of the barrier layer and of which an Al composition decreases from the barrier layer side toward a third surface side opposite to the barrier layer side;
• and
• forming a source electrode and a drain electrode, and a gate electrode provided between the source electrode and the drain electrode, on the second surface side of the barrier layer, wherein
• the forming the source electrode, the drain electrode, and the gate electrode includes forming the drain electrode and the gate electrode so that the polarization layer is provided between the gate electrode and the drain electrode, among between the gate electrode and the source electrode and between the gate electrode and the drain electrode.