Granted Patent B2

US 9,343,526 · App. 13/801,514 · Granted May 17, 2016

Abstract

Claims (15)

1. A method, comprising:

forming a buried layer over a substrate of a first conductivity type;

forming a first isolation trench around an isolated region, the isolated region being disposed over a first portion of the buried layer;

forming a second isolation trench around the first isolation trench; and

forming a punch-through structure between at least a portion of the first isolation trench and a portion of the second isolation trench by:

forming a first region over a second portion of the buried layer, the first region having the first conductivity type, and

forming a second region located over the first region, the second region having a second conductivity type.

2. The method of claim 1 , wherein, when the isolated region is set to a greater than zero potential with respect to the substrate, a voltage across the second portion of the buried layer to the substrate is less than a voltage across the first portion of the buried layer to the substrate.

3. The method of claim 1 , wherein the isolated region has a conductivity type opposite of the substrate conductivity type.

4. The method of claim 3 , including forming a second punch-through structure around the second isolation trench, the second punch-through structure including a third portion of the buried layer.

5. The method of claim 4 , wherein, when the isolated region is set to the greater than zero potential with respect to the substrate, a voltage across the third portion of the buried layer to the substrate is less than a voltage across the first portion of the buried layer to the substrate.

6. The method of claim 4 , wherein forming the second punch-through structure:

forming a third region over the third portion of the buried layer, the third region having the first conductivity type, and

forming a fourth region over the third region, the fourth region having the second conductivity type.

7. The method of claim 6 , wherein a depth of the first region of the first punch-through structure is greater than a depth of the third region of the second punch-through structure.

Assignments (30)