Patent ID: 8580690

Claim:
A process of planarizing a wafer, comprising: providing the wafer comprising a first layer and a second layer vertically on the first layer and defined into a first region and a second region laterally abutting the first region; etching the wafer to remove the second layer in the first region; forming a third layer conformally covering the first layer and the second layer; forming a blanket stop layer conformally on the third layer; performing a first chemical mechanical polishing process to completely remove the blanket stop layer atop the third layer in the second region; performing a second chemical mechanical polishing process to planarize the wafer using the blanket stop layer as a stop layer when the top surface of the second layer is lower than or at a same level as the top surface of the blanket stop layer or using the second layer as a stop layer when the top surface of the blanket stop layer is lower than or at a same level as the top surface of the second layer; and performing a third chemical mechanical polishing process to planarize the wafer to remove the remaining blanket stop layer and the third layer in the second region.