In various embodiments, a three-dimensional structured nonvolatile semiconductor memory devices and methods for manufacturing the devices are disclosed. One such device includes an n-type doped region at a source/drain region; a p-type doped region at the source/drain region; and a diffusion barrier material between the n-type doped region and the p-type doped region. The n-type doped region is substantially isolated from the p-type doped region. Other embodiments are also disclosed.