Methods for fabricating microelectronic devices with contacts to conductive staircase steps, and related devices and systems

A system, comprising:

• a three-dimensional array of memory devices comprising:
• a stack structure comprising insulative materials interleaved with conductive materials;
• a staircase structure within the stack structure and having steps comprising lateral ends of the conductive materials of the stack structure;
• contacts with different height-to-width ratios from one another, the contacts extending toward steps at upper elevations of the staircase structure;
• additional contacts extending to steps at lower elevations of the staircase structure;
• and
• conductive extensions between the steps at the upper elevations of the staircase structure and a liner material of the contacts;
• at least one processor in operable communication with the three-dimensional array of memory devices;
• and
• at least one peripheral device in operable communication with the at least one processor.

A microelectronic device, comprising:

• a staircase structure in a stack structure comprising a vertically alternating sequence of insulative material and conductive material arranged in tiers, the staircase structure comprising steps at lateral ends of the tiers of the stack structure;
• a fill material adjacent the staircase structure;
• and
• contacts extending through the fill material:
• some of the contacts extending to additional conductive material on portions of the conductive material of upper tiers of the stack structure, and
• others of the contacts extending to portions of the conductive material of lower tiers of the stack structure.