Patent ID: 8236625

Claim:
A method of forming an ESD device comprising: providing a semiconductor substrate of a first conductivity type and having first and second surfaces; forming a buffer layer of a second conductivity type on the first surface of the semiconductor substrate and having a first surface that is opposite to the first surface of the semiconductor substrate; forming a semiconductor layer of the second conductivity type overlying the first surface of the buffer layer, the semiconductor layer having a first surface that is opposite to the first surface of the buffer layer; forming a first semiconductor region of the second conductivity type and a first doping concentration positioned between the semiconductor layer and the semiconductor substrate, the first semiconductor region forming a portion of a first zener diode; forming a second semiconductor region of the second conductivity type and a second doping concentration that is greater than the first doping concentration wherein the second semiconductor region is juxtaposed to the first semiconductor region and positioned between the semiconductor layer and the semiconductor substrate, the second semiconductor region forming a portion of a second zener diode; forming a first blocking structure extending from the first surface of the semiconductor layer into the first semiconductor region wherein a periphery of the first blocking structure forms a first multiply-connected domain that surrounds at least a first portion of the first semiconductor region, the first zener diode, and a first portion of the semiconductor layer; forming a second blocking structure extending from the first surface of the semiconductor layer into the second semiconductor region wherein a periphery of the second blocking structure forms a second multiply-connected domain that surrounds at least a first portion of the second semiconductor region, the second zener diode, and a second portion of the semiconductor layer; forming a first diode in the first portion of the semiconductor layer and overlying the first semiconductor region; and forming a second diode in the second portion of the semiconductor layer and overlying the second semiconductor region.