Methods, systems, and devices for trench and pier architectures for three-dimensional memory arrays are described. A semiconductor device (e.g., a memory die) may include pier structures formed in contact with features formed from alternating layers of materials deposited over a substrate, which may provide support for subsequent processing. For example, a memory die may include alternating layers of a first material and a second material, which may be formed into various cross-sectional patterns. Pier structures may be formed in contact with the cross sectional patterns such that, when either the first material or the second material is removed to form voids, the pier structures may provide mechanical support of the cross-sectional pattern of the remaining material. In some examples, such pier structures may be formed within or along trenches or other features aligned along a direction of a memory array, which may provide a degree of self-alignment for subsequent operations.