Microelectronic devices including staircase structures and, merged source tier structures, and related memory devices and electronic systems

Abstract

A microelectronic device is disclosed, comprising: a stack structure comprising vertically alternating conductive structures and insulating structures arranged in tiers, each of the tiers individually comprising one of the conductive structures and one of the insulating structures, the stack structure having blocks separated from one another by filled slot structures; a source tier structure underlying the stack structure and comprising: a merged conductive structure adjacent a first discrete conductive structure in a first direction; and a second discrete conductive structure in the first direction that is spaced apart from the merged conductive structure by the first discrete conductive structure; a first support contact structure on the first discrete conductive structure; and a subsequent support contact structure on the merged conductive structure and adjacent the first support contact structure in the first direction, wherein one of the filled slot structures is vertically directly above at least a portion of the merged conductive structure.