Abstract
A semiconductor device includes a first and a second nitride-based semiconductor layers, a source electrode, a drain electrode, a passivation layer, a stress modulation layer and a gate electrode. The stress modulation layer is disposed over the second nitride-based semiconductor layer and extends along at least one sidewall of the passivation layer to make contact with the second nitride-based semiconductor layer, so as to form an interface. The gate electrode is disposed over the stress modulation layer and between the source and drain electrodes. The gate electrode is located directly above the interface of the stress modulation layer and the second nitride-based semiconductor layer.