Low-capacitance electro-static-discharge (ESD) protection structure with two floating wells

An Electro-Static-Discharge (ESD) input-protection device comprising:

• a p-type substrate of a semiconductor material;
• a deep N-well formed in the p-type substrate, the deep N-well having no wells taps or connections to power or ground, the deep N-well being unbiased;
• a floating P-well formed in the deep N-well, the floating P-well being shallower than the deep N-well wherein the deep N-well isolates the floating P-well from making electrical contact with the p-type substrate underneath;
• a floating N-well formed in the deep N-well, the floating N-well laterally touching the floating P-well to form a well-to-well diode;
• a P+ region contacting the floating N-well to form a P+N diode, the P+ region connected to a first terminal for receiving ESD current;
• and
• an N+ region contacting the floating P-well to form a N+P diode, the N+ region connected to a second terminal for receiving ESD current;
• wherein the floating P-well, the floating N-well, and the deep N-well have no wells taps or connections to power or ground;
• wherein the floating P-well, the floating N-well, and the deep N-well are unbiased.

A Fin Field-Effect Transistor (FinFET) Electro-Static-Discharge (ESD) protection device comprising:

• a substrate having a substantially planar surface, the substrate having a low concentration of a first dopant type;
• a plurality of fins formed on a surface of the substrate, each fin being of a semiconductor material;
• a first floating well, formed in the substrate and having a low concentration of the first dopant type;
• a second floating well, formed in the substrate and having a low concentration of a second dopant type, the second floating well and the first floating well being in contact with each other at a well-to-well junction;
• a deep well formed underneath the first floating well, and having a low concentration of the second dopant type;
• an isolating well, formed in the substrate and having a low concentration of the second dopant type;
• wherein the first floating well is isolated from the substrate by the deep well and the isolating well that surround the first floating well to prevent electrical contact with the substrate;
• a first fin in the plurality of fins, the first fin having a high concentration of the second dopant type and being formed over the first floating well having the first dopant type, wherein the first fin is in contact with the first floating well at a first junction;
• a second fin in the plurality of fins, the second fin having a high concentration of the first dopant type and being formed over the second floating well having the second dopant type, wherein the second fin is in contact with the second floating well at a second junction;
• a first electrical terminal connected to the first fin;
• and
• a second electrical terminal connected to the second fin;
• wherein an Electro-Static-Discharge (ESD) applied between the first electrical terminal and the second electrical terminal causes the well-to-well junction to punch-through and conduct in a forward-biased diode current flow.