Microelectronic devices with a polysilicon structure above a staircase structure, and related methods

A microelectronic device, comprising:

• a stack structure comprising insulative structures and conductive structures, the insulative structures and the conductive structures arranged in tiers, the conductive structures providing steps of at least one staircase structure extending at least a portion of a height of the stack structure;
• a dielectric liner substantially conforming to the steps of the at least one staircase structure;
• and
• a polysilicon fill material substantially filling a volume above the dielectric liner and the at least one staircase structure, a lower boundary of the polysilicon fill material substantially conforming to an upper boundary of the dielectric liner.

An electronic system, comprising:

• a three-dimensional array of microelectronic devices, the three-dimensional array comprising:
• a stack structure comprising a vertical sequence of tiers, the tiers individually comprising at least one conductive structure and at least one insulative structure, the stack structure defining at least one staircase with steps along horizontal ends of the conductive structures of the tiers;
• a polysilicon fill material within a volume above and having boundaries partially defined by the at least one staircase;
• a dielectric liner within the volume and between the polysilicon fill material and the at least one staircase, the dielectric liner substantially conforming to the steps of the at least one staircase;
• at least one processor in operable communication with the three-dimensional array of microelectronic devices;
• and
• at least one peripheral device in operable communication with the at least one processor.