The present disclosure provides a method for fabricating a semiconductor structure that includes a first dielectric layer over a semiconductor substrate, and a first cap layer over the first dielectric layer. The method includes forming a first metal feature in the first dielectric layer; performing a first CMP process on the first metal feature using a first rotation rate; and performing a second CMP process on the first metal feature using a second rotation rate slower than the first rotation rate. The second CMP process may be time-based. The second CMP process may stop on the first cap layer. After performing the second CMP process, the method includes removing the first cap layer. The first CMP process may have a first polishing rate to the first metal feature. The second CMP process may have a second polishing rate to the first metal feature lower than the first polishing rate.