THREE-DIMENSIONAL MEMORY DEVICE INCLUDING A MID-STACK SOURCE LAYER AND METHODS FOR FORMING THE SAME

A memory device includes a first-tier alternating stack of first insulating layers and first electrically conductive layers, a source layer overlying the first-tier alternating stack, a second-tier alternating stack of second insulating layers and second electrically conductive layers overlying the source layer, a memory opening vertically extending through the first-tier alternating stack, the source layer, and the second-tier alternating stack, a memory opening fill structure located in the memory opening and comprising a vertical stack of first memory elements and a vertical semiconductor channel vertically extending through each of the first electrically conductive layers, the source layer, and the second electrically conductive layers, and having a sidewall in contact with the source layer, and a bottom drain region in contact with a bottom portion of the vertical semiconductor channel.