Simple gate-to-drain overlapped MOSFETs using poly spacers for high immunity to channel hot-electron degradation

Short n-channel MOSFETs with permanent poly spacers over the lightly doped drain (LDD) region are demonstrated to be effective in increasing the resistance to channel hot-electron-induced degradation. The hot-electron lifetime of the poly-spacer devices is two to three orders of magnitude longer than that of a conventional oxide-spacer device. This improvement is entirely due to the reduced electron trapping in the gate oxide under the sidewall spacer. The disadvantages of the poly-spacer devices, higher gate-to-drain overlap capacitance and weaker gate oxide integrity, can both be minimized to within 20% of those of the oxide-spacer device by a short oxidation before the formation of the poly spacer.<>