An ESD protection device including a
transistor structure with resistive regions located within active areas thereof. The
transistor structure is formed of one or more MOS transistors, preferably N-type MOS transistors. The drain regions of the transistors are modified to reduce the
conductivity of those resistive regions by preventing high carrier concentration implants in one or more sections of the drain regions. This is achieved by modifying an N LDD
mask and the steps related thereto, as well as a
silicide exclusion
mask and the steps related thereto. The modifications result in the omission of N LDD
dopant from the area immediately adjacent to the underlying channel. In addition, portions of a spacer
oxide remain over the drain region to be formed. Subsequent
implant and siliciding steps are effectively blocked by the spacer
oxide that remains, leaving a low-density drain (LDD)
charge carrier concentration in those regions, except where omitted. The resistivity of those resistive LDD regions is greater than the resistivity of the adjacent portions of the drain region. The result is more uniform turn-on of ESD
transistor fingers in a protection device set without the need to add valuable
layout space and without increased
processing steps.