Patent ID: 7732287
Filing Date: 2010-06-08
Classification: H01L

Abstract:
1. A method of forming a body-tie, the method comprising: etching a first trench into a device layer of a Silicon-On-Insulator (SOI) substrate, wherein the first trench stops short of art insulating layer of the SOI substrate, and wherein the device layer underlies an STI stack comprising at least a nitride layer and an oxide layer covering the nitride layer; masking a portion of the first trench with a mask that establishes a location of the body-tie; etching a second trench into an unmasked portion of the first trench, wherein the second trench extends to the insulating layer, and wherein the nitride layer is not thinned by the etching of the second trench; forming a Shallow Trench Isolation (STI) oxide above the first and second trenches; doping drain and source regions of the device layer at a first doping density having a first average depth from a top surface of the device layer, the first average depth being less than a thickness of the STI oxide above the first trench; and doping the drain and the source regions at a second doping density having a second average depth from the top surface of the device layer, the second average depth being greater than a thickness of the STI oxide above the first trench and having a doping density that is less than a doping density of the body-tie, thereby preventing the body-tie from switching majority carrier type.