Advanced shallow trench isolation to suppress the inverse narrow channel effects for 0.24 /spl mu/m pitch isolation and beyond

A novel shallow trench isolation (STI) technique named Poly-Si-Buffered-mask STI (PB-STI) using the SiN/poly-Si/SiO/sub 2/ stacked mask has been proposed. The poly-Si is oxidized at the step of liner oxidation and then a "small bird\´s beak" is grown. With small bird\´s beak formation the oxide recess at the trench edge is prevented and the fringing of electric-field from the gate electrode can be effectively avoided. PB-STI can completely suppress the inverse narrow channel effect with quite simple process sequence which includes no corner implantation.