Double treatment on hard mask for gate n/p patterning

Abstract

The present disclosure provides a method that includes providing a semiconductor substrate having a first region and a second region, forming first and second gate stacks over the first and second regions, respectively, the first and second gate stacks each including a dummy gate electrode, removing the dummy gate electrodes from the first and second gate stacks, respectively, thereby forming trenches, forming a metal layer to partially fill the trenches, forming an oxide layer over the metal layer filling a remaining portion of the trenches, applying a first treatment to the oxide layer, forming a patterned photoresist layer on the oxide layer overlying the first region, applying a second treatment to the oxide layer overlying the second region, etching the oxide layer overlying the second region, etching the first metal layer overlying the second region, removing the patterned photoresist layer, and removing the oxide layer overlying the first region.