Methods for forming porous insulative materials for use in forming dielectric structures of semiconductor devices are disclosed. Each insulative material may include a first, substantially nonporous state and a second, porous state. When in the first state, the insulative materials may be processed or support layers or structures which are being processed. When in the second state, the insulative materials have a reduced dielectric constant and, thus, increased electrical insulation properties. Semiconductor device structures including layers or other features formed from one of the insulative materials are also disclosed. Methods for forming the insulative material and for causing the insulative material to become porous are also disclosed.