Abstract: The present disclosure describes a semiconductor structure and a method for forming the same. The semiconductor structure can include a substrate, an insulating stack formed over the substrate, a vertical structure formed through the insulating stack, a source/drain region formed over the vertical structure, and an isolation structure formed adjacent to the source/drain region and protruding the insulating stack. The source/drain region can include a first side surface and a second side surface. A lateral separation between the first side surface and the vertical structure can be greater than an other lateral separation between the second side surface and the vertical structure.