As used herein, the term “carbon-doped silicon nitride” means and includes silicon nitride (SiN) having carbon incorporated therein. The carbon is present in the silicon nitride at from about 1% by weight (wt %) to about 30 wt %. The carbon-doped silicon nitride differs from silicon carbon nitride (SiCN), which includes a stoichiometric amount of carbon, such as Si_1.5C_1.5N₄. The carbon-doped silicon nitride excludes silicon carbon nitride having a stoichiometric amount of carbon. Thus, the carbon-doped silicon nitride may include from about 1% wt % of carbon to less than about a stoichiometric amount of carbon.

As used herein, the term “selectively etchable” means and includes a material that has an etch rate that is at least about two times (2×) greater than the etch rate of another material, such as about five times (5×) greater, about ten times (10×) greater, about twenty times (20×) greater, or about forty times (40×) greater relative to the etch rate of the another material.