The invention relates to a polishing slurry for the chemical-mechanical polishing of metal and metal/dielectric structures, containing from about 2.5 to about 70% by volume of a silica sol which contains 15 to 40% by weight of SiO2 particles and is stabilized by H+ or K+ ions, wherein the SiO2 particles have a mean particle size of less than 300 nm, from about 6 to about 10% by volume of hydrogen peroxide and a base in a quantity which is appropriate to set the pH (22ºC) of the polishing slurry to from about 5 to about 1.5, has a Ta removal rate of >300 Å/min and an improved selectivity Method for making and using such a slurry.