During a fabrication of a semiconductor device, a recess is created in a substrate material disposed along a direction of a plane of fabrication. A layer of a removable material is formed in the recess. A bottom layer is formed above the layer of removable material. A vertical channel above the bottom layer is formed in a direction substantially orthogonal to the direction of the plane of fabrication. A gate is formed using a metal above the bottom layer and relative to the vertical channel. A tunnel is created under the bottom layer by removing the removable material from under the bottom layer such that the backside of the bottom layer forms a ceiling of the tunnel. The tunnel is filled using a conductive material such that the conductive material makes electrical contact with the backside of the bottom layer.