Patent ID: 9449960
Filing Date: 2016-09-20
CPC Classification: H01L

Claim Text:
1. An electrostatic discharge (ESD) protection structure, comprising: a substrate; a pick-up region, located in the substrate; a first MOS device, located on the substrate and comprising a first drain region and a first source region of a first conductivity type; a second MOS device, located on the substrate and comprising a second drain region and a second source region of the first conductivity type, wherein the first drain region is closer to the pick-up region than the second drain region is; a first doped region of a second conductivity type, located only under the first drain region; and a second doped region of the second conductivity type, located only under the second drain region, wherein an area, a doping concentration or both of the first doped region are greater than an area, a doping concentration or both of the second doped region, wherein there is only one doped region of the second conductivity type under each drain region of the first conductivity type, wherein the first doped region and the second doped region are disposed in the substrate, and a doping concentration of the first doped region and a doping concentration of the second doped region are different from a doping concentration of the substrate which surrounds the first and second doped regions.