A field plate power device comprises: a substrate; a multilayer semiconductor layer disposed on the substrate; a source electrode, a drain electrode, and a gate electrode located between the source electrode and the drain electrode disposed on the multilayer semiconductor layer; a dielectric layer disposed on the gate electrode, a part of the multilayer semiconductor layer between the gate electrode and the source electrode and another part of the multilayer semiconductor layer between the gate electrode and the drain electrode; a groove disposed in a part of the dielectric layer between the gate electrode and the drain electrode; and a field plate disposed on the groove. The field plate comprises a first portion away from the gate electrode in a horizontal direction, and the first portion has an overall upward tilted shape in the horizontal direction away from the gate electrode.