Formation of transistor gates

Abstract

A method comprises forming first and second fins each comprising alternately stacking first and second semiconductor layers; forming dummy gate structures over the first and second fins, and gate spacers on either side of the dummy gate structures; removing the dummy gate structures to form first and second gate trenches; removing the first semiconductor layers such that the second semiconductor layers are suspended in the first and second gate trenches; depositing a first dielectric layer around the second semiconductor layers and a second dielectric layer around the first dielectric layer; performing an ALD process to form a hard mask layer around the second dielectric layer, the ALD process comprising pulsing a first precursor for a first pulse time longer than about one second; patterning the hard mask layer; and etching a portion of the second gate dielectric layer in the second gate trench.