A stairless electrical interconnect structure with contact pillars embedded within and collectively accessing each tier in a periodic material stack, e.g., to provide electrical connections to access lines associated with a three-dimensional memory array, is described. The contact pillars can be formed in a corresponding array of vertical contact pillar trenches etched into the material stack in two stages to create depths of the trenches that vary between columns by a fixed number of tiers and then offset the depths between rows.