MICROELECTRONIC DEVICES INCLUDING STAIR STEP STRUCTURES, AND RELATED ELECTRONIC SYSTEMS AND METHODS

A microelectronic device includes a stack structure including a vertically alternating sequence of conductive structures and insulating structures arranged in tiers, a dielectric-filled opening vertically extending into the stack structure and defined between two internal sidewalls of the stack structure, a stadium structure within the stack structure and comprising steps defined by horizontal ends of at least some of the tiers, a first ledge extending upward from a first uppermost step of the steps of the stadium structure and interfacing with a first internal sidewall of the two internal sidewalls of the stack structure, and a second ledge extending upward from a second, opposite uppermost step of the steps of the stadium structure and interfacing with a second, opposite internal sidewall of the two internal sidewalls.