Transistor having wrap-around source/drain contacts

Abstract

Embodiments of the invention are directed to a field effect transistor (FET) device including a first channel region over a first region of a substrate; a second channel region over a second region of the substrate and adjacent to the first channel region; and a bottom conductive layer over a third region of the substrate and operable to form a bottommost component of a multi-component wrap-around source or drain (S/D) contact. The first region of the substrate, the second region of the substrate, and the third region of the substrate do not overlap. The bottom conductive layer includes a non-uniform height having a first section and a second section. The first section tapers downward toward the first channel region and the second section tapers downward toward the second channel region.

What is claimed is: 
     
         1 . A field effect transistor (FET) device comprising:
 a first channel region over a first region of a substrate;   a second channel region over a second region of the substrate and adjacent to the first channel region; and   a bottom conductive layer over a third region of the substrate and operable to form a bottommost component of a multi-component wrap-around source or drain (S/D) contact;   wherein the first region of the substrate, the second region of the substrate, and the third region of the substrate do not overlap;   wherein the bottom conductive layer includes a non-uniform height having a first section and a second section; and   wherein the first section tapers downward toward the first channel region and the second section tapers downward toward the second channel region.   
     
     
         2 . The device of  claim 1  further comprising:
 a shared S/D region between the first channel region and the second channel region and over the bottom conductive layer; 
 wherein the shared S/D region is not a component of the multi-component S/D contact; 
 wherein the shared S/D region is communicatively coupled to the first channel region, the second channel region, and the bottom conductive layer; 
 wherein the shared S/D region is formed subsequently to forming the bottom conductive layer; and 
 wherein the first section tapers downward toward the first channel region and the second section tapers downward toward the second channel region such that:
 portions of the bottom conductive layer that are closest to the first channel region do not contact a first sidewall of the first channel region; and 
 portions of the bottom conductive layer that are closest to the second channel region do not contact a first sidewall of the second channel region. 
 
 
     
     
         3 . The device of  claim 2  further comprising:
 a top S/D contact region over the shared S/D region and operable to form an upper component of the multi-component wrap-around S/D contact; 
 wherein the top S/D contact region is communicatively coupled to the bottom conductive layer such that the top S/D contact region coupled to the bottom conductive layer defines a central opening; and 
 wherein the central opening is occupied by the shared S/D region. 
 
     
     
         4 . The device of  claim 3 , wherein:
 the bottom conductive layer comprises a first conductive material;   the top S/D contact region comprises a second conductive material; and   the first conductive material is different than the second conductive material.   
     
     
         5 . The device method of  claim 3 , wherein a surface area of an interface between the wrap-around S/D contact and the shared S/D region comprises:
 a first surface area of an interface between the shared S/D region and a first portion of a top surface of the bottom conductive layer; and   a second surface area of an interface between the top S/D contact region and the shared S/D region.   
     
     
         6 . The device of  claim 3 , wherein the shared S/D region is communicatively coupled to the bottom conductive layer through a first region of the top surface of the bottom conductive layer. 
     
     
         7 . The device of  claim 6 , wherein the top S/D contact region is communicatively coupled to the bottom conductive layer through a second region of the top surface of the bottom conductive layer. 
     
     
         8 . The method of  claim 1 , wherein:
 the first section that tapers downward toward the first channel region reduces a first capacitance between a first gate of the first channel and a shared S/D region over the bottom conductance layer; and   the second section that tapers downward toward the second channel region reduces a second capacitance between a second gate of the second channel and the shared S/D region over the bottom conductance layer.   
     
     
         9 . The device of  claim 3 , wherein:
 the top S/D contact region comprises:
 a contact liner; 
 a barrier liner; and 
 a conductive metal. 
   
     
     
         10 . A set of semiconductor devices comprising:
 a channel region over a first region and a second region of a substrate;   a bottom conductive layer over a third region of the substrate and operable to form a bottommost component of a multi-component wrap-around source or drain (S/D) contact;   wherein the first region of the substrate, the second region of the substrate, and the third region of the substrate do not overlap; and   a shared S/D region over the bottom conductive layer and adjacent to the channel region;   wherein the channel region comprises a first channel stack over the first region of the substrate and a second channel stack over the second region of the substrate;   wherein the first channel stack comprises a first set of stacked and spaced-apart channel nanosheets;   wherein the second channel stack comprises a second set of stacked and spaced-apart channel nanosheets;   wherein the shared S/D region is shared by the first channel stack and the second channel stack;   wherein a non-uniform height of the bottom conductive layer tapers downward for portions of the bottom conductive layer that are closest to the first channel stack;   wherein the non-uniform height of the bottom conductive layer tapers downward for portions of the bottom conductive layer that are closest to the second channel stack; and   wherein the shared S/D region is not a component of the multi-component S/D contact.   
     
     
         11 . The device of  claim 10  further comprising:
 a top S/D contact region over the shared S/D region and operable to form an upper component of the multi-component wrap-around S/D contact; and 
 wherein the top S/D contact region is communicatively coupled to the bottom conductive layer such that the top S/D contact region coupled to the bottom conductive layer defines a central opening; 
 wherein the central opening is occupied by the shared S/D region.