Cyclical deposition method and apparatus for filling a recess formed within a substrate surface

There is provided a method of filling one or more recesses by providing the substrate in a reaction chamber; introducing a first reactant, to form first active species, for a first pulse time to the substrate; introducing a second reactant for a second pulse time to the substrate; and introducing a third reactant, to form second active species, for a third pulse time to the substrate. An apparatus for filling a recess is also disclosed and a structure formed using the method and/or apparatus is disclosed.