Diode RF sputtering technique has been used to produce carbon-tungsten ultra thin layers stacks for application in the soft X-ray domain as optical system. In situ kinetic ellipsometry has been chosen to control the multilayers growth with a great accuracy. Grazing X-ray reflection (1.54 P., absolute soft X-ray reflectivity (44.7 Å) and cross section transmission electron microscopy results confirm a posteriori the ellipsometry ones. Deposition conditions have been optimized using these characterizations. The thick-ness fluctuations are very low (0.2 % per layer). We have observed the smoothing of the layers roughness as the number of C-W sequences increases (the substrate having a roughness of 7 Å, the layers of 2 Å). We have realized multilayers in the range 2d = 60 Å and 2d = 90 Å. Their reflectivities typically reach 8 % = 45° at 44.7 Å) for the first ones and 13 % (9- = 30° at 44.7 Å) for the second ones. We have also realized stacks with a great number of layers in the range 2d = 100 A. 17 % reflectivities have been reached for a 180 layers stack.