Apparatus with multidielectric spacers on conductive regions of stack structures, and related methods

Apparatus (e.g., semiconductor devices) include stack structures with at least one conductive region and at least one nonconductive material. A multidielectric spacer is adjacent the at least one conductive region and comprises first and second dielectric materials. The first dielectric material, adjacent the at least one conductive region, includes silicon and nitrogen. The second dielectric material, adjacent the first dielectric material, comprises silicon-carbon bonds and defines a substantially straight, vertical, outer sidewall. In methods to form such apparatus, the first dielectric material may be formed with selectivity on the at least one conductive region, and the second dielectric material may be formulated and formed to exhibit etch resistance.