Methods of forming microelectronic devices, and related microelectronic devices, memory devices, and electronic systems each with a filled trench within a stadium structure of at least one block

A method of forming a microelectronic device, comprising:

• forming a preliminary stack structure comprising a vertically alternating sequence of sacrificial material and insulative material arranged in tiers, the preliminary stack structure further comprising a stadium structure comprising opposing staircase structures having steps comprising edges of the tiers of the preliminary stack structure;
• forming a filled trench vertically over and within a horizontal area of the stadium structure, the filled trench comprising:
• a first dielectric liner structure comprising a first dielectric material extending continuously over surfaces of the preliminary stack structure within the horizontal area of the stadium structure;
• a second dielectric liner structure comprising a second dielectric material having a different material composition than the first dielectric material extending continuously over surfaces of the first dielectric liner structure;
• a third dielectric liner structure comprising the first dielectric material extending continuously over surfaces of the second dielectric liner structure;
• a fourth dielectric liner structure comprising the second dielectric material extending continuously over surfaces of the third dielectric liner structure;
• and
• a dielectric fill material overlying the fourth dielectric liner structure;
• a second dielectric fill material over the second dielectric liner structure;
• forming contact structures within the horizontal area of the stadium structure, the contact structures vertically extending completely through the filled trench and each of the tiers of the preliminary stack structure underlying the filled trench;
• and
• replacing the sacrificial material of the tiers of the preliminary stack structure with conductive material after forming the contact structures.

A memory device, comprising:

• a stack structure comprising tiers each comprising a conductive material and an insulative material vertically neighboring the conductive material, the stack structure divided into blocks extending in parallel in a first direction and separated from one another in a second direction by dielectric slot structures, each of the blocks comprising a stadium structure comprising opposing staircase structures individually having steps comprising horizontal ends of at least some the tiers of the stack structure;
• filled trenches within the blocks of the stack structure, each of the filled trenches vertically over and within a horizontal area of the stadium structure of one of the blocks of the stack structure and comprising:
• an alternating sequence of dielectric liner structures and additional dielectric liner structures, the dielectric liner structures having a different material composition than the additional dielectric liner structures;
• and
• a dielectric fill material vertically overlying and horizontally surrounded by the alternating sequence of the dielectric liner structures and the additional dielectric liner structures;
• and
• strings of memory cells vertically extending through a portion of each of the blocks neighboring the stadium structure in the first direction.