Nitridization of the stacked poly-si gate to suppress the boron penetration in pMOS

NH3 -nitridation to create nitrogen-rich layers inbetween the stacked layers of the poly-Si gate for pMOS application is proposed and demonstrated. Due to the blocking of fluorine diffusion in the poly-Si gate by the nitrogen-rich layers, the amount of fluorine in the gate oxide, consequently, the fluorine enhancement on boron penetration is reduced. The negative effects of the NH3 -nitridized oxide were not found in this work. Moreover, this nitridized stacked poly-Si gate improves significantly the electrical characteristics of the gate oxide as a result of the indirect and slight nitridation at the gate oxide.