The present invention relates to a semiconductor device with an asymmetric gate structure. The device comprises a substrate; a channel layer, positioned above the substrate; a barrier layer, positioned above the channel layer, the barrier layer and the channel layer being configured to form two-dimensional electron gas (2DEG), and the 2DEG being formed in the channel layer along an interface between the channel layer and the barrier layer; a source contact and a drain contact, positioned above the barrier layer; a doped group III-V layer, positioned above the barrier layer and between the drain contact and the source contact; and a gate electrode, positioned above the doped group III-V layer and configured to form a Schottky junction with the doped group III-V layer, wherein the doped group III-V layer and/or gate electrode has a non-central symmetrical geometry so as to achieve the effect of improving gate leakage current characteristics.