The present invention provides an improved surface P-channel transistor and a
method of making the same. A preferred embodiment of the method of the present
invention includes providing a semiconductor substrate, forming a gate oxide layer
over the semiconductor substrate, subjecting the gate oxide layer to a remote plasma
nitrogen hardening treatment followed by an oxidative anneal, and forming a polysilicon
layer over the resulting gate oxide layer. Significantly, the method of the present
invention does not require nitrogen implantation through the polysilicon layer
overlying the gate oxide and provides a surface P-channel transistor having a polysilicon
electrode free of nitrogen and a hardened gate oxide layer characterized by a large
concentration of nitrogen at the polysilicon electrode/gate oxide interface and
a small concentration of nitrogen at the gate oxide/semiconductor substrate interface.
The method of the present invention is easily incorporated into known fabrication
processes and provides an enhanced surface P-channel transistor that resists hot
electron degradation, is substantially impermeable to dopants included in overlying
layers, and is characterized by a greatly increased extrapolated time dependent
dielectric breakdown value.