Gate-oxide degradation from source/drain (S/D) boron diffusion

Boron diffusion from p/sup +/-poly gate through thin gate oxide not only causes a transistor to degrade, but also reduces the reliability of the thin gate-oxide. This problem has been studied extensively. Since high concentration of boron is used in the S/D of p-MOSFET, it has long been speculated that boron diffusion from S/D can also cause gate-oxide reliability problem. However, such a degradation mode has never been reported. In this paper, we report clear evidence of such degradation and show that boron diffusion from S/D sets a limit to spacer thickness scaling.