One inventive aspect is related to an atomic layer deposition (ALD) method comprising: a) providing a semiconductor substrate in a reactor, b) providing a pulse of a first precursor gas into the reactor at a first temperature, c) providing a first pulse of a second precursor gas into the reactor at a second temperature, and d) providing a second pulse of the second precursor gas at a third temperature lower than the second temperature. Another inventive aspect relates to a reactor suitable to apply the method.