A silicon nitride comprising layer formed over a semiconductor substrate includes Al, Ga or a mixture thereof. A silicon dioxide comprising layer is formed proximate thereto. The silicon dioxide comprising layer is removed substantially selectively relative to the silicon nitride comprising layer, with the Al, Ga or a mixture thereof enhancing selectivity to the silicon nitride comprising layer during the removal. A substantially undoped silicon dioxide comprising layer formed over a semiconductor substrate includes B, Al, Ga or mixtures thereof. A doped silicon dioxide comprising layer is formed proximate thereto. The doped silicon dioxide comprising layer is removed substantially selectively relative to the substantially undoped silicon dioxide comprising layer, with the B, Al, Ga or mixtures thereof enhancing selectivity to the substantially undoped silicon dioxide comprising layer during the removal. Integrated circuitry is also disclosed.