Self-aligned backside contact with increased contact area

Abstract

A first and a second source drain region, an upper source drain contact connected to the first source drain region, a bottom source drain contact connected to the second source drain region, a dielectric spacer surrounds opposite vertical side surfaces of the bottom source drain contact and overlaps a vertical side surface and a lower horizontal surface of a bottom isolation region. A width of the bottom source drain contact wider than a width of the second source drain. Forming an undoped silicon buffer epitaxy in an opening between and below a first and a second nanosheet stack, forming a contact to a first source drain adjacent to that, removing the undoped silicon buffer epitaxy below a second source drain between the first and the second nanosheet stack, forming a bottom contact to that, a width of the bottom contact is wider than a width of the second source drain.