Field effect transistor with non-floating body and method for forming same on a bulk silicon wafer

Claim 1

A method of forming a field effect transistor on a semiconductor substrate, comprising of: a) etching an insulating trench around the perimeter of an active region of said transistor to isolate the active region from other structures on said substrate; b) etching an insulating undercut in the bottom of the insulating trench to isolate at least a portion of the bottom surface of the active region from the substrate; and c) doping portion of the active region to from each of a source region and a drain region on opposing side of a central channel region, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping from a conductive bridge between the central channel region and the substrate.

Claim 2

A method of forming a field effect transistor on a semiconductor substrate, comprising of: a) etching an insulating trench around the perimeter of an active region of said transistor to isolate the active region from other structures on said substrate; b) etching an insulating undercut in the bottom of the insulating trench to isolate at least a portion of the bottom surface of the active region from the substrate; and c) doping portion of the active region to from each of a source region and a drain region on opposing side of a central channel region, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping from a conductive bridge between the central channel region and the substrate.

Claim 15

A method of forming a field effect transistor on a semiconductor substrate, comprising the steps of: a) etching an insulating trench around the perimeter of an active region of said transistor to isolate the active region from other structures on said substrate; b) etching an insulating undercut in the bottom of the insulating trench to isolate at least a portion of the bottom surface of the active region from the substrate, including: i) forming a protective layer on the side walls and bottom of trench; ii) performing a vertical anisotropic etch of said layer to remove such layer to expose the semiconductor substrate at the bottom of the trench; and iii) performing an isotropic etch of the semiconductor substrate to form said undercut; c) forming a gate on the active region; d) doping portions of the active region to form each of a source region and a drain region on opposing sides of a central channel region, wherein the gate acts as a mask for the doping, thereby defining the central channel region and aligning the source region and the gate region with the gate, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping form a conductive bridge between the central channel region and the substrate.

Claim 16

A method of forming a field effect transistor on a semiconductor substrate, comprising the steps of: a) etching an insulating trench around the perimeter of an active region of said transistor to isolate the active region from other structures on said substrate; b) etching an insulating undercut in the bottom of the insulating trench to isolate at least a portion of the bottom surface of the active region from the substrate, including: i) forming a protective layer on the side walls and bottom of trench; ii) performing a vertical anisotropic etch of said layer to remove such layer to expose the semiconductor substrate at the bottom of the trench; and iii) performing an isotropic etch of the semiconductor substrate to form said undercut; c) forming a gate on the active region; d) doping portions of the active region to form each of a source region and a drain region on opposing sides of a central channel region, wherein the gate acts as a mask for the doping, thereby defining the central channel region and aligning the source region and the gate region with the gate, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping form a conductive bridge between the central channel region and the substrate.

Claim 22

A method of forming a field effect transistor, comprising: a) etching an insulating trench in a semiconductor substrate to define an active region therein; b) forming an insulating undercut in the bottom of the insulating trench to isolate a portion of the bottom surface of the active region from a remainder of the substrate, including: i) forming a protective layer on the side walls and bottom of trench; ii) performing a vertical anisotropic etch of said layer to remove such layer to expose the semiconductor substrate at the bottom of the trench; and iii) performing an isotropic etch of the semiconductor substrate to form the undercut; c) forming a gate on the active region; d) doping portions of the active region to form each of a source region and a drain region on opposing sides of a central channel region, wherein the gate acts as a mask for the doping, thereby defining the central channel region and aligning the source region and the gate region with the gate, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping form a conductive bridge of semiconductor material between the central channel region and the remainder of the substrate, thereby leaving an electrical connector between the central channel region and the remainder of the substrate via the conductive bridge; and wherein the conductive bridge has a smaller cross-sectional area than the central channel region.

Claim 23

A method of forming a field effect transistor, comprising: a) etching an insulating trench in a semiconductor substrate to define an active region therein; b) forming an insulating undercut in the bottom of the insulating trench to isolate a portion of the bottom surface of the active region from a remainder of the substrate, including: i) forming a protective layer on the side walls and bottom of trench; ii) performing a vertical anisotropic etch of said layer to remove such layer to expose the semiconductor substrate at the bottom of the trench; and iii) performing an isotropic etch of the semiconductor substrate to form the undercut; c) forming a gate on the active region; d) doping portions of the active region to form each of a source region and a drain region on opposing sides of a central channel region, wherein the gate acts as a mask for the doping, thereby defining the central channel region and aligning the source region and the gate region with the gate, wherein the insulating undercut isolates at least a portion of both the source region and the drain region from the semiconductor substrate, and wherein the undercut isolates at least a portion of the central channel region from the semiconductor substrate, the undercut extending under the central channel region in a direction from the source region to the drain region; wherein the etching the undercut and the doping form a conductive bridge of semiconductor material between the central channel region and the remainder of the substrate, thereby leaving an electrical connector between the central channel region and the remainder of the substrate via the conductive bridge; and wherein the conductive bridge has a smaller cross-sectional area than the central channel region.