Suppression of Boron Penetration in P-Channel MOSFETs Using Polycrystalline Si1 x yGexCy Gate Layers

Boron penetration through thin gate oxides in p-channel MOSFETs with heavily boron-doped gates causes undesirable positive threshold voltage shifts. P-channel MOSFETs with polycrystalline Si1 x yGexCy gate layers at the gate-oxide interface show substantially reduced boron penetration and increased threshold voltage stability compared to devices with all poly Si gates or with poly Si1 xGex gate layers. Boron accumulates in the poly Si1 x yGexCy layers in the gate, with less boron entering the gate oxide and substrate. The boron in the poly Si1 x yGexCy appears to be electrically active, providing similar device performance compared to the poly Si or poly Si1 xGex gated devices.