Patent ID: 8193473

Claim:
A heating unit comprising: a base having an upper surface on which an object to be processed is placed, the upper surface including an inner peripheral part and an outer peripheral part, with the outer peripheral part being an area between an outer edge of the upper surface and an outer perimeter of a concentric circle whose radius is shorter than that of the upper surface by approximately 30%, and the inner peripheral part being an area that is radially within the area of the outer peripheral part; a first resistive heating element buried in an upper part of the base, the upper part including the upper surface, the first resistive heating element having a flat shape essentially parallel to the upper surface; and a second resistive heating element buried in a lower part of the base and arranged in a location lower than the first resistive heating element with respect to the upper surface in a direction orthogonal to the upper surface, the lower part being joined to the upper part, and the second resistive heating element having a flat shape, wherein a first projection pattern and a second projection pattern have an overlapping portion where the first projection pattern and the second projection pattern partially overlap each other, the first projection pattern representing the first resistive heating element projected on the upper surface of the base, and the second projection pattern representing the second resistive heating element projected on the upper surface of the base, an occupation ratio of an aggregate area of the first projection pattern and the second projection pattern to an area of the upper surface is 85% to 100%, an overlap ratio, defined as a ratio of an area of the overlapping portion to an area of the second projection pattern in the upper surface is, from 20% to 30% in the outer peripheral part and 5% to 20% in the inner peripheral part.