An electrostatic chuck for attracting an object for treatment. The electrostatic chuck includes a substrate, an insulating dielectric layer and at least one electrode located between the substrate and the insulating dielectric layer. The object is attracted onto the electrode via the insulating dielectric layer. The insulating dielectric layer is between 0.5 mm and 5.0 mm thick, and utilizes a gas-introducing hole to form a gas-diffusing depression on the side of an attractive surface, allowing for more uniform heat conduction. The gas-diffusing depression is between 100 um and 5.0 mm deep. The distance between the bottom surface of the gas-diffusing depression and an electrode may range from 500 .mu.m to 5 mm.