Methods of forming microelectronic devices including support contact structures

A method of forming a microelectronic device, comprising:

• forming a preliminary stack structure comprising tiers vertically stacked relative to one another and respectively comprising insulative material and additional insulative material vertically neighboring the insulative material, the preliminary stack structure overlying a source structure and divided into blocks separated from one another by slots, at least one of the blocks comprising:
• stadium structures including staircase structures having steps comprising edges of at least some of the tiers;
• and
• crest regions interposed between horizontally alternating with the stadium structures;
• forming contact structures extending through the tiers of the preliminary stack structure, the contact structures comprising:
• conductive contact structures within the crest regions of the blocks and individually extending completely through the tiers of the preliminary stack structure and to the source structure;
• and
• semiconductive contact structures within the crest regions of the blocks and individually extending completely through the tiers of the preliminary stack structure and to the source structure;
• and
• replacing at least a portion of the additional insulative material of respective ones of the tiers of the preliminary stack structure with conductive material after forming the contact structures.

A method of forming a microelectronic device, comprising:

• forming blocks over a source structure and individually including a vertically alternating sequence of oxide material and nitride material arranged in tiers, the blocks separated from one another by slots and respectively comprising:
• stadium structures individually comprising staircase structures having steps comprising horizontal ends of the tiers;
• crest regions horizontally interposed between neighboring ones of the stadium structures in a first direction;
• and
• bridge regions horizontally interposed between the stadium structures and the slots in a second direction orthogonal to the first direction;
• forming first contact structures within the crest regions of the blocks and individually including conductive material vertically extending through the tiers and to the source structure;
• forming second contact structures neighboring the first contact structures within the crest regions of the blocks and individually including polycrystalline silicon material extending through the tiers and to the source structure;
• and
• replacing the nitride material of the tiers of the blocks with additional conductive material after forming the first contact structures and the second contact structures.