Microelectronic devices including isolation structures neighboring staircase structures, and related memory devices, electronic systems, and methods

A microelectronic device, comprising:

• a stack structure comprising alternating conductive structures and insulative structures arranged in tiers;
• a stair step structure within the stack structure and having steps comprising horizontal ends of the tiers;
• support pillar structures extending through the stack structure;
• a first insulative material vertically overlying the stair step structure and defining a seam within the first insulative material;
• conductive contact structures extending through the first insulative material, each of the conductive contact structures in electrical communication with a step of the stair step structure;
• and
• isolation structures comprising a second insulative material extending through the first insulative material and at least partially filling the seam and electrically isolating horizontally neighboring conductive contact structures from each other.

A method of forming a microelectronic device, the method comprising:

• forming a first insulative material over a staircase structure in a stack structure comprising a vertically alternating sequence of conductive structures and insulative structures arranged in tiers, the first insulative material defining a seam extending in a first horizontal direction;
• forming support pillar structures through the stack structure, the seam between support pillar structures horizontally neighboring one another in a second horizontal direction;
• forming trenches through at least a portion of the first insulative material and exposing portions of the seam;
• filling at least a portion of the seam and the trenches with a second insulative material;
• and
• forming conductive contact structures through the first insulative material and in electrical communication with steps of the staircase structure, the first insulative material and the second insulative material electrically isolating neighboring conductive contact structures from one another.

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, the at least one microelectronic device structure comprising:
• a staircase structure within a stack structure comprising a vertically alternating sequence of conductive structures and insulative structures arranged in tiers;
• a first insulative material vertically overlying the staircase structure;
• support pillar structures extending through the stack structure, the support pillar structures arranged in columns and rows;
• and
• isolation structures comprising a second insulative material, the isolation structures located between a first column of the columns of the support pillar structures and a second column of the columns of the support pillar structures, a portion of the isolation structures extending horizontally between a support pillar structure of the first column and a support pillar structure of the second column, the isolation structures within the first insulative material and vertically extending at least partially into the first insulative material.