pH-buffered slurry and use thereof for polishing

A multistep method for polishing a surface which comprises polishing said surface by first contacting it with a first slurry comprising abrasive particles and having a pH of about 1 to about 6 and contacting and polishing the surface having the slurry thereon with a polishing pad;

• followed by providing on said surface a second and different slurry comprising abrasive particles, a pH of about 3 to about 11 and a pH buffering component comprising at least one acid or salt thereof or mixture thereof in a concentration of about 10−5 M to about 102 M and at least one base or salt thereof or mixture thereof in a concentration of about 10−5 M to about 102 M and wherein the buffering component of the second slurry is free of metal cations, and polishing said surface having said second slurry thereon by contacting it with a polishing pad, wherein said acid and/or said base also acts as a complexing agent for metal cations.