The embedded SCR NMOS and low capacitance ESD protection device

Inserting the n-well and p+ diffusion into the drain region of NMOS transistor, the embedded SCR NMOS (ESCR NMOS), without changing any DC I-V characteristics of NMOS, and a very low capacitance (/spl sim/50 fF) ESD protection (LCESD) device are developed successfully for output pad and input pad, respectively. In addition, a protection scheme, combining the power protection device and a n+ guard-ring, is proposed and proven to be capable of protecting four directions ESD zapping and without increasing the LCESD device capacitance.