Memory circuitry and method used in forming memory circuitry

Abstract

Memory circuitry comprising strings of memory cells comprises a stack comprising vertically-alternating insulative tiers and conductive tiers. Channel-material strings of memory cells extend through the insulative tiers and the conductive tiers in a memory-array region. The insulative tiers and the conductive tiers extend from the memory-array region into a stair-step region. The stair-step region comprises a cavity comprising a flight of stairs extending along a first direction. Multiple different-depth and height-sequential treads in individual of the stairs extend along a second direction that is orthogonal to the first direction. Individual of the multiple different-depth treads comprise conducting material of one of the conductive tiers. The cavity comprises a pair of laterally-opposing outermost sidewalls relative to the second direction and that individually extend along the first direction. The multiple different-depth and height-sequential treads in the individual stairs comprise a single flight of said treads that extends along the second direction from one of the laterally-opposing outermost sidewalls to the other of the laterally-opposing outermost sidewalls. Methods are disclosed.