In a method of depositing a crystalline germanium layer on a substrate, a substrate is placed in the process zone comprising a pair of process electrodes. In a deposition stage, a crystalline germanium layer is deposited on the substrate by introducing a deposition gas comprising a germanium-containing gas into the process zone, and forming a capacitively coupled plasma of the deposition gas by coupling energy to the process electrodes. In a subsequent treatment stage, the deposited crystalline germanium layer is treated by exposing the crystalline germanium layer to an energized treatment gas or by annealing the layer.