A microelectronic device includes a stack structure including blocks separated from one another by dielectric slot structures and each including a vertically alternating sequence of conductive structures and insulative structures arranged in tiers. The blocks including a stadium structure including opposing staircase structures each having steps comprising edges of the tiers. The blocks further include a filled trench vertically overlying and within horizontal boundaries of the stadium structure. The filled trench includes dielectric liner structures and additional dielectric liner structures having a different material composition than that of the dielectric liner structures and alternating with the dielectric liner structures. The filled trench also includes dielectric fill material overlying an alternating sequence of the dielectric liner structures and additional dielectric liner structures.