An Asymmetric Effect of Short Channel MOSFETs

So far, MOSFET source and drain have been considered to be symmetric in view of geometry as well as electric characteristics in practical devices. However, when source and drain were exchanged, a difference was detected in the electrical characteristics for MOSFETs with shallow junctions with an angled arsenic ion implantation. This phenomenon (referred to an asymmetric effect) was quite marked not in threshold voltage but in ID-VD characteristics for shorter channel length MOSFETs. And its amounts for MOSFETs with channel length (L≤2.5um) become 10 to 20%. So the asymmetric effect can be a serious problem for a VLSI made from these short cannel devices.