| CPC H10B 41/27 (2023.02) [H10B 41/10 (2023.02); H10B 41/35 (2023.02); H10B 43/10 (2023.02); H10B 43/27 (2023.02); H10B 43/35 (2023.02); H10D 30/6891 (2025.01); H10D 30/694 (2025.01)] | 20 Claims | 

| 
               1. A three-dimensional memory device, comprising: 
            an alternating stack of insulating layers and word-line-level electrically conductive layers; 
                a vertical layer stack located over the alternating stack, the vertical layer stack comprising multiple levels of drain select electrodes and multiple levels of drain-select-level insulating layers that are vertically interlaced; 
                a spacer insulating layer located between the alternating stack and the vertical layer stack, the spacer insulating layer having a thickness which is greater than a thickness of each of the respective insulating layers in the alternating stack, and is greater than a thickness of each of the respective drain-select-level insulating layers; 
                drain-select-level isolation structures laterally extending along a first horizontal direction such that drain select electrodes located at a same level are laterally spaced apart from each other by the drain-select-level isolation structures; 
                memory openings vertically extending through the vertical layer stack, the spacer insulating layer, and the alternating stack; and 
                memory opening fill structures located in the memory openings and comprising a respective vertical semiconductor channel and a respective memory film, wherein the three-dimensional memory device further comprises at least one feature selected from: 
                a first feature wherein each of the drain-select-level isolation structures is in direct contact with a respective drain select electrode at each of the levels of the drain select electrodes; or 
                a second feature wherein three-dimensional memory device further comprises a contact-level dielectric layer overlying the vertical layer stack and drain contact via structures vertically extending through the contact-level dielectric layer, wherein: top surfaces of the drain-select-level isolation structures are located within a horizontal plane including a top surface of the contact-level dielectric layer; each of the memory opening fill structures comprises a respective drain region; and top surfaces of the drain contact via structures are located within the horizontal plane including the top surface of the contact-level dielectric layer. 
               |