Ceramic heater

A ceramic heater comprising:

• a disc-shaped ceramic plate having a wafer mounting surface, the disc-shaped ceramic plate being divided into small inner circumferential side zone and a circular ring-shaped outer circumferential side zone;
• a cylindrical shaft connected to a rear surface of the ceramic plate, the rear surface being on an opposite side of the wafer mounting surface;
• an inner circumferential side resistance heating element which is embedded in the small inner circumferential size zone of the ceramic plate;
• an outer circumferential side resistance heating element which is embedded in the circular ring-shaped outer circumferential side zone of the ceramic plate;
• a shaft inside area which is of the rear surface of the ceramic plate and inside of the cylindrical shaft;
• a hole which is provided along a direction deviated from a diameter direction of the ceramic plate and extends from the shaft inside area to a predetermined position of the circular ring-shaped outer circumferential side zone of the ceramic plate;
• and
• attached components which are provided in the shaft inside area and include a pair of terminals of the inner circumferential side resistance heating element and a pair of terminals of the outer circumferential side resistance heating element,
• wherein a portion of the hole forms a groove, the portion of the hole forming the groove passing through the shaft inside area,
• the attached components are collectively provided in one of two division areas which are in the shaft inside area and divided by an axial line of the groove, the one having a larger area, and
• wherein the entire groove is linear in a cross-sectional view and a plan view.