Nitride-based semiconductor device and method for manufacturing the same

A nitride-based semiconductor device, comprising:

• a first nitride-based semiconductor layer;
• a second nitride-based semiconductor layer disposed on the first nitride-based semiconductor layer and having a bandgap higher than a bandgap of the first nitride-based semiconductor layer;
• a source electrode and a drain electrode disposed above the second nitride-based semiconductor layer;
• a gate electrode disposed above the second nitride-based semiconductor layer and between the source and drain electrodes;
• a doped nitride-based semiconductor layer disposed between the second nitride-based semiconductor layer and the gate electrode;
• and
• a first field plate disposed over the doped nitride-based semiconductor layer, wherein a vertical projection of the doped nitride-based semiconductor layer on the second nitride-based semiconductor layer overlaps with a vertical projection of the first field plate on the second nitride-based semiconductor layer, and a vertical projection of the gate electrode on the second nitride-based semiconductor layer is physically separated from the vertical projection of the first field plate on the second nitride-based semiconductor layer,
• wherein a bottom of the doped nitride-based semiconductor layer comprises a main body portion, a first portion and a second portion, the main body portion overlaps with the gate electrode, the first portion and the second portion do not overlap with the gate electrode and continuously extend toward the source electrode and the drain electrode, respectively, from the main body portion, a first horizontal distance between a side of the gate electrode close to the drain electrode and a side of the second portion close to the drain electrode is greater than a second horizontal distance between a side of the gate electrode close to the source electrode and a side of the first portion close to the source electrode, and a thickness of at least one of the first portion and the second portion is less than a thickness of the main body portion.