Semiconductor device and power amplifier

A semiconductor device, comprising:

• a substrate;
• a buffer layer disposed on the substrate;
• a channel layer disposed on the buffer layer;
• a barrier layer disposed on the channel layer;
• a gate electrode disposed on the barrier layer;
• a source electrode disposed on the barrier layer at a first side of the gate electrode;
• a drain electrode disposed on the barrier layer at a second side of the gate electrode opposite to the first side of the gate electrode, wherein a spike region is formed below at least one of the source electrode and the drain electrode, the spike region extends into the buffer layer through the barrier layer and the channel layer;
• and
• a passivation layer disposed on the barrier layer and extending onto sidewalls and top surfaces of the source electrode and the drain electrode, wherein the passivation layer has an opening, the gate electrode is disposed in the opening and protruded from the opening.