Memory arrays and methods of their formation are disclosed. One such memory array has memory-cell strings are formed adjacent to separated substantially vertical, adjacent semiconductor structures, where the separated semiconductor structures couple the memory cells of the respective strings in series. For some embodiments, two dielectric pillars may be formed from a dielectric formed in a single opening, where each of the dielectric pillars has a pair of memory-cell strings adjacent thereto and where at least one memory cell of one of the strings on one of the pillars and at least one memory cell of one of the strings on the other pillar are commonly coupled to an access line.