Abstract: An electrostatic chuck for electrostatically clamping a semiconductor wafer while minimizing any plane temperature difference thereof has a dielectric layer joined to a metal plate and an inner electrode disposed in the di-electric layer. The dielectric layer has a raised outer rim disposed on an upper surface thereof along an outer peripheral edge thereof, and a plurality of protrusions disposed on the upper surface radially inwardly of the outer rim, the protrusions having upper surfaces for clamping the semiconductor wafer in direct contact therewith. The volume resistivity of the dielectric layer is 10.sup.9 .OMEGA.m or less, and Rmax (maximum height) of the clamping surfaces of the protrusions 5 is 2.0 .mu.m or less and or Ra (center-line average roughness) thereof is 0.25 .mu.m or less. The ratio of the total area of the clamping surfaces of the protrusions to the entire area of the upper surface of the dielectric layer is equal to or greater than 1% and less than 10%.