Heater unit for semiconductor processing

In a heater unit, comprising a lower metallic base, an upper metallic base placed closely over an upper surface of said lower base, and a resistance heater wire received in a groove defined between opposing surfaces of said lower and upper bases, ceramic powder is filled in said groove to keep said heater wire at least away from a wall surface of said groove. Thus, the heater wire can be directly installed in the groove of the base without the intervention of a sheath pipe so that the heater wire can be bent in a desired dense pattern, and the heater unit can be heated both rapidly and uniformly. Also, the ceramic powder filled in the groove improves the heat transfer, and this even further enhances the these advantages of the present invention.