Programmable metallization memory cells having a first metal contact and a second metal contact with an ion conductor solid electrolyte material between the metal contacts. The first metal contact has a filament placement structure thereon extending into the ion conductor material. In some embodiments, the second metal contact also has a filament placement structure thereon extending into the ion conductor material toward the first filament placement structure. The filament placement structure may have a height of at least about 2 nm.