Patent ID: 8288815

Claim:
A gate structure for a semiconductor device, the gate structure comprising: a conductive structure disposed over a substrate, the conductive structure comprising: a middle portion having a first surface and two second surfaces, wherein the first surface is between the two second surfaces; and two conductive spacer portions respectively connected to the two second surfaces of the middle portion, wherein a width of each of the two conductive spacer portions gradually increases from top to bottom, wherein an inner surface of each of the two conductive spacer portions contacts with the middle portion, and an outer surface of each of the two conductive spacer portions opposite the inner surface of each of the two conductive spacer portions is a curved surface; and a mask layer disposed on the middle portion of the conductive structure, wherein two sides of the mask layer are respectively enclosed by the two conductive spacer portions of the conductive structure so that the mask layer is embedded into the conductive structure.