embodiment, which will not be described below, are identical to those of the previously-described embodiment shown in FIG. 18, and will not be described repetitively. 

[0276] As shown in FIG. 34, sponges 687, each serving as a liquid-retaining member, are provided in through-holes 101a of polishing pad 101. These sponges 687 have lower ends contacting base 654b of support member 654, and have upper ends positioned above polishing surface of the polish› ing pad 101. The sponges 687 are made from a deformable material, so that polishing head 1, holding the substrate W, can compress the sponges 687 via the substrate W to allow the substrate W to contact the polishing surface during polishing. With this structure, the electrolytic solution is retained by the sponges 687 during polishing. Hence, an amount of the elec› trolytic solution scattering off the polishing surface due to a centrifugal force can be reduced. 

[0277] On the other hand, when dressing the polishing sur› face, the above-described clamp is removed, and as shown in FIG. 35, lid 654a is elevated so that the upper ends of the sponges 687 are positioned below the polishing surface. In this state, the lid 654a and the base 654b are fixed in position. Then, while a pure-water supply nozzle 688 supplies pure water onto the polishing surface, the dresser 218 dresses the polishing surface. Because the dresser 218 does not contact the sponges 687 during dressing, the sponges 687 are not damaged by the dresser 218. 

[0278] Other than the sponge, a fibrous memberor an open› cell foam may be used for the liquid-retaining member. An example of a method of forming the open-cell foam includes the steps of mixing fine particles of calcium carbonate with a base material, injection-molding the base material mixed with the calcium carbonate particles to form an injection› molded product, and immersing the injection-molded prod› uct into hydrochloric acid water to decompose and dissolve the calcium carbonate particles. In this case, an amount of the calcium carbonate particles, filling the base material, is required to be large enough to allow the calcium carbonate particles to be in contact with each other. As the base material, polyurethane, polyolefin, or rubber can be used. 

[0279] FIG. 36 is a schematic cross-sectional view showing another example of this embodiment. As shown in FIG. 36, in this example, the electrolytic-solution path for directing the electrolytic solution to the through-holes 101a from below the polishing pad 101 is not provided. Instead, the electrolytic solution is supplied directly onto the polishing surface from the electrolytic-solution supply nozzle 102. Sponges 687, each serving as the liquid-retaining member, are provided in the through-holes 101a, respectively, so that the electrolytic solution, supplied from the electrolytic-solution supply nozzle 102, is retained by the sponges 687. 

[0280] In this example, it is preferable that the upper ends of the sponges 687 be positioned below the polishing surface so as not to interfere with dressing of the polishing surface. An arrangement of the liquid-retaining members is not limited to the above examples in which the liquid-retaining members are disposed in the through-holes 101a which are uniformly distributed over the polishing surface. For example, the pol› ishing surface may have grooves on its upper surface (i.e., polishing surface), and the liquid-retaining members may be disposed in these grooves. In this case, the arrangements of the liquid-retaining members as viewed from above include a linear arrangement, a concentric circular arrangement, and a fan-shaped arrangement. 

[0281] FIG. 37 and FIG. 38 are cross-sectional views each schematically showing an example of a polishing pad 101 used in an electrochemical mechanical polishing apparatus 250 according to still another embodiment of the present invention. Components and operations of this embodiment, which will not be described below, are identical to those of the previously-described embodiment shown in FIG. 18, and will not be described repetitively. 

[0282] In this embodiment, each of through-holes 101a has an upper opening with a smaller diameter than a diameter of a lower opening thereof More specifically, in the example shown in FIG. 37, the diameter of each of the through-holes 101a is gradually decreased from the lower opening to the upper opening. In the example shown in FIG. 38, each of the through-holes 1 Ola has two holes arranged vertically in series with different diameters. Because the upper opening is smaller than the lower opening, the electrolytic solution retained in the through-holes 101a is prevented from scatter› ing due to a centrifugal force. In this embodiment, the elec› trolytic-solution path for directing the electrolytic solution to the through-holes 101a from below polishing pad 101 may not be provided. Instead, the electrolytic solution may be supplied directly onto the polishing surface from electrolytic› solution supply nozzle 102 so that the through-holes 101a retain the electrolytic solution therein. 

[0283] FIG. 39 is a schematic cross-sectional view showing an electrochemical mechanical polishing apparatus 250 according to still another embodiment of the present inven› tion. Components and operations of this embodiment, which will not be described below, are identical to those of the previously-described embodiment shown in FIG. 18, and will not be described repetitively. 

[0284] As shown in FIG. 39, an annular gas passage 690 is provided so as to surround polishing pad 101. This gas pas› sage 690 has a slit (i.e., gas ejection opening) 691 in an inner circumferential surface thereof, so that a gas, flowing through the gas passage 690, is ejected through the slit 691 toward a centerof polishing surface of the polishing pad 101. With this gas passage 690, the gas can push back the electrolytic solu› tion that is about to flow out from the polishing surface by a centrifugal force. The gas ejection opening is not limited to the slit. Plural holes ( each having a diameter of not more than 1 mm, for example) may be provided as the gas ejection opening. In this embodiment, the electrolytic-solution path for directing the electrolytic solution to the through-holes 1 Ola from below the polishing pad 101 may not be provided. Instead, the electrolytic solution may be supplied directly onto the polishing surface from electrolytic-solution supply nozzle 102. Further, a conductive pad may be used for the polishing pad 101, and the second electrode (electric supply electrode) may be in contact with the conductive pad so as to supply an electric current to the conductive film on the sub› strate via the conductive pad. 

[0285] FIG. 40 is a schematic side view showing an elec› trochemical mechanical polishing apparatus 250 according to still another embodiment of the present invention. Compo› nents and operations of this embodiment, which will not be described below, are identical to those of the previously› described embodiment shown in FIG. 18, and will not be described repetitively. 

[0286] As shown in FIG. 40, two cylindrical rollers 693 and 694, each rotatable about its own axis, are provided laterally to polishing pad 101. These rollers 693 and 694 are operable to sandwich the overhanging polishing head 1 during polish- 

