A three-dimensional memory device including multiple stack structures can be formed with a joint region electrode, which is an electrode formed at a joint region located near the interface between an upper stack structure and a lower stack structure. A memory stack structure is formed through the multiple stack structures. The joint region electrode laterally surrounds a portion of the memory stack structure in proximity to the interface between different stack structures. The joint region electrode includes a layer portion having a thickness and a collar portion that laterally surrounds the memory stack structure and having a greater vertical extent than the thickness of the layer portion. The increased vertical extent of the collar portion with respect to the vertical extent of the layer portion provides enhanced control of a portion of a semiconductor channel in the memory stack structure located near the interface between different stack structures.