A semiconductor memory device comprises a memory block including conductive layers at different levels from a substrate and separated from each other by a first insulation material. A memory pillar extends through the first conductive layers. A hookup region is adjacent to the memory block and includes conductive layers stacked on the substrate at levels from the substrate that corresponds to the conductive layers in the memory block. An isolation region is between the memory block and the hookup region and includes first insulating layers of a second insulating material different than the first insulating material. Each first insulating layer is at a level from the substrate that corresponds to one of the first conductive layers and each first insulating layer is between one of the conductive layers in the memory block and one of the conductive layers in hookup region.