Gate-fringing field effects on high performance in high dielectric LDD spacer MOSFETs

Both n- and p-channel MOSFETs with high dielectric LDD spacer material (HLDD) were investigated. As the dielectric constant of the LDD spacer becomes higher, the gate-fringing field increases, resulting in drain electric field reduction. Therefore, the impact ionization rate can be reduced in both n- and p-channel HLDD due to small source parasitic resistance in the HLDD caused by the large gate-fringing field effects (GF effects). On the other hand, in the p-channel HLDD, transconductance is not enhanced, because of large parasitic resistance at the LDD p^- junction edge. It is also shown that gate-fringing field effects have much more influence on the LDD MOSFET performance in scaling down the transistor´s dimensions and the packing density in MOSFETs