Abstract: There is provided a method of filling one or more recesses by providing the substrate in a reaction chamber and introducing a first reactant to the substrate with a first dose, introducing a second reactant to the substrate with a second dose, wherein the first and the second doses overlap in an overlap area where the first and second reactants react and leave an initially substantially unreacted area where the first and the second areas do not overlap; introducing a third reactant to the substrate with a third dose, the third reactant reacting with the first or second reactant to form deposited material; and etching the deposited material. An apparatus for filling a recess is also disclosed.