A microelectronic device having a stack structure with an alternating sequence of conductive material and insulative material arranged in tiers, and having blocks separated by dielectric slot structures. Each of the blocks has a stadium structure, a filled trench overlying the stadium structure, support structures extending through the filled trench and tiers of the stack structure, and dielectric liner structures covering sidewalls of the support structures. The stadium structure has staircase structures each having steps with edges of the tiers of the stack structure. The filled trench has a dielectric material interposed between at least two additional dielectric materials. The dielectric liner structures have first protrusions at vertical positions of the dielectric material, and second protrusions at vertical positions of the conductive material of the tiers of the stack structure. The second protrusions have greater horizontal dimensions that the first protrusions. Memory devices, electronic systems, and methods are also described.