Structure and Formation Method of Semiconductor Device with Conductive Feature

A structure and a formation method of a semiconductor device are provided. The method includes forming a conductive feature over a semiconductor substrate and forming a dielectric layer over the conductive feature. The method also includes forming an opening in the dielectric layer to expose the conductive feature. The method further includes forming a conductive material to overfill the opening. In addition, the method includes thinning the conductive material using a chemical mechanical polishing process. A slurry used in the chemical mechanical polishing process includes an iron-containing oxidizer that oxidizes a portion of the conductive material.