The invention discloses a manufacture method of a metallic gate structure. The method comprise steps of: providing a substrate, wherein a dielectric layer is arranged on the substrate, a first trench and a second trench are arranged in the dielectric layer and are fully filled with a first metallic layer and a second metallic layer respectively, and the width of the first trench is less than that of the second trench; forming a mask layer in order to completely cover the second trench; performing a first etching technique under the covering of the mask layer in order to remove a part of the first metallic layer; and performing a second etching technique in order to simultaneously remove a part of the first metallic layer and a part of the second metallic layer.