US 5,675,166 A · FET with stable threshold voltage and method of manufacturing the same

Abstract

A low voltage field effect transistor structure (20) is provided with a threshold voltage that is tolerant of process variations that alter the location of a source implant region (41). A first halo region (33) and a second halo region (36) are formed adjacent to source region (41) such that after subsequent thermal processing, a constant doping profile of opposite conductivity as source region (41) is formed in the channel region (23) adjacent the source region (41). The embodiments can be formed either adjacent to only the source region (41) to create a unilateral device, or the doping profile can be formed adjacent to both source region (41) and a drain region (40) to produce a bilateral device. An additional embodiment forms a second implant region in source region (41) to reduce junction leakage and capacitance.

Claims16

Dependent claims

A field effect transistor having stable threshold voltage comprising:

a substrate region of a semiconductor material of a first conductivity type and having a surface;
a source region of a second conductivity type formed in the substrate region and adjacent to a channel region;
a first implant region disposed in the substrate region such that first implant region is contiguous with the source region at the surface and extends into the channel region below the surface of the substrate region, the first implant region having a first concentration of the first conductivity type;
and
a second implant region disposed between the source region and the first implant region extending beyond the first implant region at the surface and into the channel region, wherein the first implant region and the second implant region form a first dopant profile region of constant doping at an intersection with the source region and in a portion of the substrate region adjacent to the source region, the second implant region having a second concentrating of the first conductivity type.

2 more elements

A low voltage unilateral field effect transistor having a robust threshold voltage and punchthrough resistance provided by a plurality of halo regions comprising:

a body of a semiconductor material of a first conductivity type and having a first major surface;
a gate structure formed on the first major surface, the gate structure having a first edge and a second edge;
a source region of a second conductivity type formed in the body of the semiconductor material contiguous with the first edge of the gate structure and extending from the first major surface;
a drain region of said second conductivity type formed in the body of the semiconductor material contiguous with the second edge of the gate structure and extending from the first major surface wherein a portion of the body of semiconductor material separates the source region from the drain region to provide a channel region;
a plurality of halo regions of the first conductivity type aligned to the first edge of the gate structure and formed in the body of the semiconductor material such that the plurality of halo regions form a dopant profile that is essentially constant where the dopant profile contacts and is adjacent to the source region;
a first electrode coupled to the source region;
a second electrode coupled to the drain region;
and
a third electrode coupled to the gate structure.

6 more elements

Dependencies are inferred from the claim text.

FET with stable threshold voltage and method of manufacturing the same

Life of this patent

FET with stable threshold voltage and method of manufacturing the same

Life of this patent

Abstract

Claims16