Integrated circuit comprising a MOS transistor having a sigmoid response and corresponding method of fabrication

1. An integrated circuit comprising:

at least one metal oxide semiconductor (MOS) transistor comprising

a substrate,

a source region and a drain region spaced apart on said substrate,

a gate between said source region and said drain region, wherein a dimension of said gate extending between said source region and said drain region is less than or equal to twenty eight nanometers,

a channel region in the substrate beneath the gate and between the source and drain regions, and

a respective insulating spacer on opposing sides of said gate,

said substrate having respective separator regions under each insulating spacer and separating the source region and the drain region from the channel region so that the channel region is not in physical contact with either the drain region or the source region, the channel region and the separator regions having a same conductivity type, and wherein the separator regions define respective energy barriers in the substrate such that for a constant gate-source voltage the at least one MOS transistor has a sigmoidal drain-source voltage,

said source and drain regions comprising only metal layers on said substrate and without doped source and drain regions in said substrate.

2. The integrated circuit of claim 1 wherein the channel region and the separator regions have a P-type conductivity.

3. The integrated circuit of claim 1 wherein the at least one MOS transistor comprises a plurality thereof interconnected to define an artificial neural network.

4. An integrated circuit comprising:

a plurality of metal oxide semiconductor (MOS) transistors interconnected to define an artificial neural network, each MOS transistor comprising

a substrate,

a source region and a drain region spaced apart on said substrate,

a gate between said source region and said drain region, wherein a dimension of said gate extending between said source region and said drain region is less than or equal to twenty eight nanometers,

a channel region in the substrate beneath the gate and between the source and drain regions, and

a respective insulating spacer on opposing sides of said gate,

said substrate having a respective separator region under each of said insulating spacers and separating said source region and said drain region from the channel region so that the channel region is not in physical contact with either the drain region or the source region, the channel region and the separator regions having a same conductivity type, and wherein the separator regions define respective energy barriers in the substrate such that for a constant gate-source voltage the MOS transistor has a sigmoidal drain-source voltage,

said source and drain regions comprising only metal layers on said substrate and without doped source and drain regions in said substrate.

5. A metal oxide semiconductor (MOS) transistor comprising:

a substrate;

a source region and a drain region spaced apart on said substrate;

a gate between said source region and said drain region, wherein a dimension of said gate extending between said source region and said drain region is less than or equal to twenty eight nanometers;

a channel region in the substrate beneath the gate and between the source and drain regions; and

a respective insulating spacer on opposing sides of said gate;

said substrate also having respective separator regions under each insulating spacer and separating the source region and the drain region from the channel region so that the channel region is not in physical contact with either the drain region or the source region, the channel region and the separator regions having a same conductivity type, and wherein the separator regions define respective energy barriers in the substrate such that for a constant gate-source voltage the MOS transistor has a sigmoidal drain-source voltage;

said source and drain re ions comprising only metal layers on said substrate and without doped source and drain regions in said substrate.

6. The MOS transistor of claim 5 wherein the channel region and the separator regions have a P-type conductivity.

7. A method of making a metal oxide semiconductor (MOS) transistor comprising:

forming a source region and a drain region spaced apart on a substrate with a channel region in the substrate beneath the gate and between the source and drain regions, the substrate having respective separator regions between the source region and the drain region, the separator regions separating the source region and the drain region from the channel region so that the channel region is not in physical contact with either the drain region or the source region, and the channel region and separator regions having a same conductivity type;

forming a gate between the source region and the drain region on the substrate and over the channel region, wherein a dimension of the gate extending between the source region and the drain region is less than or equal to twenty eight nanometers; and

forming insulating spacers on opposing sides of the gate region with each insulating spacer being over a respective separator region so that the separator regions separate the source region and the drain region from the first region, and wherein the separator regions define respective energy barriers in the substrate such that for a constant gate-source voltage the MOS transistor has a sigmoidal drain-source voltage,

wherein the source and drain regions comprise only metal layers on the substrate and without doped source and drain regions in said substrate.

8. The method of claim 7 wherein forming the source and drain regions comprises forming the source and drain regions by depositing at least one of layer of metal and performing a silicidation of the at least one layer of metal.

9. The method of claim 7 wherein the channel region and the separator regions have a P-type conductivity.