Microelectronic devices including staircase structures, and related memory devices and electronic systems

A memory device, comprising:

• a stack structure comprising vertically alternating conductive structures and insulating structures arranged in tiers, each of the tiers individually comprising at least one of the conductive structures and at least one of the insulating structures;
• a staircase structure having steps comprising edges of at least some of the tiers of the stack structure;
• a source tier underlying the stack structure and comprising:
• a source plate;
• and
• discrete conductive structures horizontally separated from one another and the source plate by a dielectric material;
• contact structures on the steps of the staircase structure;
• support structures horizontally between the contact structures and vertically extending through the stack structure to the discrete conductive structures of the source tier;
• data lines overlying the stack structure;
• an array of vertically extending strings of memory cells extending through the stack structure and electrically connected to the source plate and the data lines;
• conductive lines electrically connected to the contact structures;
• and
• a control device vertically underlying the source tier and within horizontal boundaries of the array of vertically extending strings of memory cells, the control device electrically coupled to the source plate, the data lines, and the conductive lines.

An electronic system, comprising:

• an input device;
• an output device;
• a processor device operably coupled to the input device and the output device;
• and
• a memory device operably coupled to the processor device and comprising at least one microelectronic device structure comprising:
• a stack structure comprising tiers each comprising an electrically conductive structure and a dielectric structure vertically neighboring the electrically conductive structure;
• a staircase structure within the stack structure and exhibiting steps comprising edges of at least some of the tiers;
• a source tier vertically below the stack structure and comprising:
• a source structure;
• and
• discrete conductive structures electrically isolated from one another and the source structure;
• and
• conductive contact structures on the steps of the staircase structure;
• and
• conductive support pillars having oblong horizontal cross-sectional shapes horizontally alternating with the conductive contact structures and vertically extending through the stack structure at the staircase structure to the discrete conductive structures of the source tier.