A method of fabricating a substrate includes forming spaced first features over a substrate. An alterable material is deposited over the spaced first features and the alterable material is altered with material from the spaced first features to form altered material on sidewalls of the spaced first features. A first material is deposited over the altered material, and is of some different composition from that of the altered material. The first material is etched to expose the altered material and spaced second features comprising the first material are formed on sidewalls of the altered material. Then, the altered material is etched from between the spaced second features and the spaced first features. The substrate is processed through a mask pattern comprising the spaced first features and the spaced second features. Other embodiments are disclosed.