Local gate height tuning by cmp and dummy gate design

Abstract

The present disclosure describes fabricating devices with tunable gate height and effective capacitance. A method includes forming a first metal gate stack in a dummy region of a semiconductor substrate, the first metal gate stack including a first work function metal (WFM) layer; forming a second metal gate stack in an active device region of the semiconductor substrate, the second metal gate stack including a second WFM layer different than the first WFM layer; and performing a CMP process using a slurry including charged abrasive nanoparticles. The charged abrasive nanoparticles include a first concentration in the active device region different from a second concentration in the dummy region causing different polish rates in the active device region and dummy region. After the performing of the CMP process, the first metal gate stack has a first height different from a second height of the second metal gate stack.