Integrated stacked ESD network in trench for trench DMOS

A stacked Electrostatic Discharge (ESD) structure, comprising:

• a heavily doped substrate acting as a drain;
• an epitaxial layer grown on the substrate;
• a trench formed in the epitaxial layer;
• an oxide layer formed on an inner sidewall of the trench;
• a first poly layer formed in the trench;
• a plurality of P-type regions and N-type regions formed inside the first poly layer to make back to back diodes in the first poly layer;
• a dielectric layer formed in the trench, on top of the first poly layer;
• a second poly layer formed in the trench, on top of the dielectric layer;
• a plurality of P-type regions and N-type regions formed inside the second poly layer to make back to back diodes and poly resistors in the second poly layer;
• an insulating layer formed on top of the second poly layer and the trench;
• a plurality of contacts defined to connect the first poly layer, the poly resistor and the second poly layer, through the insulating layer;
• and
• a metal layer formed on top of the insulating layer.