fixed to the polishing-head drive shaft 11, and driven pins (not shown) fixed to the housing 2a. The driving pins and the driven pins are vertically movable relative to each other. Accordingly, even when the head body 2 is tilted, the pins still engage each other, with contact points of the pins being shifted. The rotation transmitting mechanism thus securely transmits the torque of the polishing-head drive shaft 11 to the head body 2. 

[0128] In the space formed in the head body 2 and the retainer ring 3 fixed integrally to the head body 2, there are housed an elastic pad 4 to be in contact with the substrate W, an annular holder ring 5, and a substantially disk-shaped chucking plate 6 for supporting the elastic pad 4. The elastic pad 4 is sandwiched, at its peripheral portion, between the holder ring 5 and the chucking plate 6 fixed to a lower end of the holder ring 5. The elastic pad 4 is shaped so as to cover a lower surface of the chucking plate 6. A space is thus formed between the elastic pad 4 and the chucking plate 6. 

[0129] A pressure sheet 7, composed of an elastic mem› brane, is provided so as to stretch between the holder ring 5 and the head body 2. One end of the pressure sheet 7 is sandwiched between the housing 2a and the pressure-sheet support 2b of the head body 2, and another is sandwiched between an upper end portion Sa and a stopper portion Sb of the holder ring 5. A pressure chamber 21 is formed inside the head body 2. This pressure chamber 21 is defined by the head body 2, the chucking plate 6, the holder ring 5, and the pressure sheet 7. The pressure chamber 21 is located above the chucking plate 6. As shown in FIG. 5, a fluid passage 31, which comprises a tube and connectors, is provided so as to communicate with the pressure chamber 21. The pressure chamber 21 is coupled to the compressed air source 120 via a regulator RE2 provided in the fluid passage 31. The pressure sheet 7 is made from, for example, a rubber material having excellent strength and durability, such as ethylene-propylene rubber (EPDM), polyurethane rubber, or silicon rubber. 

[0130] If the pressure sheet 7 is made from an elastic mate› rial, such as rubber, and is sandwiched between the retainer ring 3 and the head body 2, a desirable flat plane may not be obtained in the lower surface of the retainer ring 3, because of elastic deformation of the elastic pressure sheet 7. In order to avoid such a drawback, the pressure-sheet support 2b is sepa› rately provided, according to this embodiment, so as to sand› wich and fix the pressure sheet 7 between the housing 2a and the pressure-sheet support 2b of the head body 2. 

[0131] It is possible to make the retainer ring 3 vertically movable relative to the head body 2 or to make the retainer ring 3 operable to press the polishing pad 101 independent of the head body 2, as disclosed in Japanese Patent Application No. 8-50956 (Laid-Open Publication No. 9-168964) or Japa› nese Patent Application No. 11-294503. In such a case, the above-described structure of fixing the pressure sheet 7 may not necessarily be employed. 

[0132] A center bag (a central contact member) 8 and a ring tube ( an outer contact member) 9, which are contact members to be in contact with the elastic pad 4, are provided in the space formed between the elastic pad 4 and the chucking plate 6. As shown in FIGS. 5 and 6, in this embodiment, the center bag 8 is disposed on the central portion of the lower surface of the chucking plate 6, and the ring tube 9 is disposed outside of the center bag 8 so as to surround the center bag 8. The elastic pad 4, the center bag 8, and the ring tube 9 are made from rubber having excellent strength and durability, such as eth- 

ylene-propylene rubber (EPDM), polyurethane rubber, or silicon rubber, as with the pressure sheet 7. 

[0133] The space formed between the chucking plate 6 and the elastic pad 4 is divided by the center bag 8 and the ring tube 9 into plural chambers: a pressure chamber 22 formed between the center bag 8 and the ring tube 9; and a pressure chamber 23 formed outside the ring tube 9. 

[0134] The center bag 8 comprises an elastic membrane 81, which is to be in contact with an upper surface of the elastic pad 4, and a center bag holder (holding member) 82 detach› ably holding the elastic membrane 81. The center bag holder 82 has screw holes 82a formed therein. Screws 55 are inserted into the screw holes 82a to thereby allow the center bag 8 to be detachably mounted on the central portion of the lower surface of the chucking plate 6. Inside the center bag 8, a central pressure chamber 24 is defined by the elastic mem› brane 81 and the center bag holder 82. 

[0135] Similarly, the ring tube 9 comprises an elastic mem› brane 91, which is to be in contact with the upper surface of the elastic pad 4, and a ring tube holder (holding member) 92 detachably holding the elastic membrane 91. The ring tube holder 92 has screw holes 92a formed therein. Screws 56 are inserted into the screw holes 92a to thereby allow the ring tube 9 to be detachably mounted on the lower surface of the chucking plate 6. Inside the ring tube 9, an intermediate pressure chamber 25 is defined by the elastic membrane 91 and the ring tube holder 92. 

[0136] Fluid passages 33, 34, 35, and 36, each including a tube and connectors, are provided so as to communicate with the pressure chambers 22 and 23, the central pressure cham› ber 24, and the intermediate pressure chamber 25, respec› tively. The pressure chambers 22 to 25 are coupled to the compressed air source 120 as a pressurized-fluid supply source via regulators RE3, RE4, RES, and RE6 respectively provided in the fluid passages 33-36. The above-described fluid passages 31, 33-36 are coupled to the respective regu› lators RE2-RE6 via rotary joints (not shown) provided at an upper end of the polishing-head drive shaft 11. 

[0137] A pressurized fluid (e.g., pressurized air) is to be supplied to the above-described pressure chambers 21-25, or atmospheric pressure or vacuum is to be produced in the pressure chambers 21-25 via the fluid passages 31, 33-36. As shown in FIG. 4, the pressures of pressurized fluids to be supplied to the pressure chambers 21-25 can be adjusted by the regulators RE2-RE6 provided in the fluid passages 31, 33-36. The pressures in the pressure chambers 21-25 can thus be controlled independently, or atmospheric pressure or vacuum can be produced in the pressure chambers 21-25. 

[0138] In this manner, by changing the pressures in the pressure chambers 21-25 independently via the regulators RE2-RE6, the elastic pad 4 can press the substrate W against the polishing pad 101 with pressing forces adjusted for respective portions ( divisional areas) of the substrate W. The pressure chambers 21-25 may be coupled to a vacuum source 121, as desired. 

[0139] As shown in FIG. 4, the upper surface of the polish› ing table 100 of the electrochemical mechanical polishing apparatus 250 is covered with a disk-shaped insulating plate 252, and a first electrode (cathode) 256, coupled to one of poles of a power source 254, is disposed on an upper surface of the insulating plate 252. In this embodiment, the first electrode 256 is comprised of plural (three) ring-shaped divided electrodes 256a to 256c which are concentrically arranged. A cylindrical core 258 is disposed in a center of the 

