The invention discloses a
semiconductor device and a manufacturing method thereof. The
semiconductor device comprises a substrate, a
semiconductor layer located on the substrate, a source and a drain located on the semiconductor layer, a gate located between the source and the drain, a
source field plate located on the semiconductor layer and connected with the source, wherein the
source field plate passes across the gate, the gate / source region and part of the gate / drain region, and air isolation is carried out; one end of the
source field plate is connected with the source; two or more than two
metal field plates are connected in parallel to form connection between the source field plate and the source; and the other end of the source field plate is located on the semiconductor layer, close to the gate, between the gate and the drain. A role of
electric field modulation of the source field plate can be fully played, parasitic gate / source
capacitance and parasitic conduction resistance can be fully reduced, and reliability of the device is improved.