A semiconductor structure comprises a substrate comprising an interlayer dielectric (ILD) and a silicon layer disposed over the ILD, wherein the ILD comprises a conductive structure disposed therein, a dielectric layer disposed over the silicon layer, and a conductive plug electrically connected with the conductive structure and extended from the dielectric layer through the silicon layer to the ILD, wherein the conductive plug has a length extending from the dielectric layer to the ILD and a width substantially consistent along the length.