| CPC H01L 29/2003 (2013.01) [H01L 29/66462 (2013.01); H01L 29/7787 (2013.01)] | 19 Claims |

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1. A nitride-based semiconductor device, comprising:
a first nitride-based semiconductor layer having at least one trench;
a second nitride-based semiconductor layer disposed on the first nitride-based semiconductor layer and spaced apart from the trench, wherein the second nitride-based semiconductor layer has 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, so as to at least define a drift region between the gate electrode and the drain electrode and overlapping with the trench;
a third nitride-based semiconductor layer at least disposed in the trench and extending upward from the trench to make contact with the second nitride-based semiconductor layer, wherein the third nitride-based semiconductor layer has a bandgap higher than the bandgap of the first nitride-based semiconductor layer; and
a dielectric layer disposed above the second nitride-based semiconductor layer and covers the gate electrode, wherein the third nitride-based semiconductor layer further extends upward to a position higher than the dielectric layer.
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