Memory Arrays Comprising Strings Of Memory Cells And Methods Used In Forming A Memory Array Comprising Strings Of Memory Cells

A method used in forming a memory array comprising strings of memory cells, comprising:

• forming a conductor tier comprising conductor material on a substrate;
• forming a lower portion of a stack that will comprise vertically-alternating first tiers and second tiers above the conductor tier, the stack comprising laterally-spaced memory-block regions, material of the first tiers being of different composition from material of the second tiers, a lowest of the first tiers comprising sacrificial material;
• forming sacrificial pillars in the conductor tier in locations where individual channel-material strings will be formed and forming islands in the conductor tier that are individually directly under individual of the sacrificial pillars, the islands comprising a composition other than that of the conductor material there-above and other than that of the sacrificial pillars;
• forming the vertically-alternating first tiers and second tiers of an upper portion of the stack above the lower portion and the sacrificial pillars;
• etching channel openings through the first tiers and the second tiers that are individually directly above and stop on the individual sacrificial pillars;
• removing the sacrificial pillars to extend the channel openings to the islands;
• forming a channel-material-string construction in individual of the channel openings and that extends to be directly against individual of the islands;
• forming horizontally-elongated trenches into the stack that are individually laterally-between immediately-laterally-adjacent of the memory-block regions, the trenches extending through the upper portion to the lowest first tier and exposing the sacrificial material therein;
• isotropically etching the exposed sacrificial material from the lowest first tier through the trenches;
• and
• after the isotropically etching, forming conductive material in the lowest first tier that directly electrically couples together the channel material of the channel-material-string constructions and the conductor material of the conductor tier.

A memory array comprising strings of memory cells, comprising:

• laterally-spaced memory blocks individually comprising a vertical stack comprising alternating insulative tiers and conductive tiers above a conductor tier, strings of memory cells comprising channel-material-string constructions that extend through the insulative tiers and the conductive tiers into the conductor tier, the channel material of the channel-material-string constructions directly electrically coupling to conductor material of the conductor tier;
• the conductor tier comprising islands comprising material of different composition from that of the conductor material of the conductor tier that surrounds individual of the islands, the islands being directly against bottoms of the channel-material-string constructions;
• and
• intervening material laterally-between and longitudinally-along immediately-laterally-adjacent of the memory blocks.