Methods of forming and tuning a multilayer select device are provided, along with apparatus and systems which include them. As is broadly disclosed in the specification, one such method can include forming a first region having a first conductivity type; forming a second region having a second conductivity type and located adjacent to the first region; and forming a third region having the first conductivity type and located adjacent to the second region and, such that the first, second and third regions form a structure located between a first electrode and a second electrode, wherein each of the regions have a thickness configured to achieve a current density in a range from about 1×e4 amps/cm2 up to about 1×e8 amps/cm2 when a voltage in a selected voltage range is applied between the first electrode and the second electrode.