Memory Circuitry And Method Used In Forming Memory Circuitry

A method used in forming memory circuitry comprises forming a stack comprising vertically-alternating first tiers and second tiers directly above a conductor tier. The first tiers comprise sacrificial material and the second tiers comprise non-sacrificial material that is of different composition from that of the sacrificial material. The stack comprises horizontally-elongated trenches extending through the first tiers and the second tiers and are individually between immediately-laterally-adjacent memory-block regions. Channel-material strings are formed that extend through the first and second tiers in the memory-block regions. Through the horizontally-elongated trenches, the sacrificial material is replaced with conductive material that comprises control-gate lines in the memory-block regions. After the replacing, conducting material is formed in a lowest of the first tiers and directly electrically couples together the channel material of the channel-material strings and conductor material of the conductor tier. Other embodiments, including structure, are disclosed.