Abstract
A semiconductor device includes first and second nitrogen-based semiconductor layers and a gate structure. The gate structure includes an outer spacer, an inner spacer, and a gate electrode. The outer spacer has at least two opposing inner sidewalls to define a gate trench. The inner spacer is located in the gate trench. A gate electrode is disposed within the gate trench and covered by the inner spacer, where the inner spacer and the gate electrode extend downwardly to collectively form a bottom of the gate structure, the bottom having a first width greater than a second width of a bottom surface of the gate electrode.