An integrated circuit device includes an insulating structure, a first source/drain region on the insulating structure, a second source/drain region on the insulating structure and spaced apart from the first source/drain region, a gate structure including at least one gate electrode layer, the gate structure being between the first source/drain region and the second source/drain region, a contact plug connected to the gate structure, a first backside source/drain contact structure penetrating the insulating structure and connected to the first source/drain region, an electrical insulating layer on a side wall of an end portion of the first backside source/drain contact structure, the electrical insulating layer contacting the first source/drain region, and a first semiconductor material layer on the electrical insulating layer, where the electrical insulating layer is configured to electrically insulate the first semiconductor material layer from the first backside source/drain contact structure.

A quantum device formed from a substrate, the substrate being covered with a semiconductor region forming a quantum dot, and a detection structure with a Coulomb blockade for detecting a state of charge of the quantum dot, the detection structure with the Coulomb blockade including a detection island disposed above and facing the quantum dot and coupled to the quantum dot by electrostatic coupling, the detection structure further including a first tunnel junction between the detection island and a first gate block, the first gate block being juxtaposed with the detection island.