disposed on the body member the wafer support containing a plurality of troughs which extend along the surface thereof a plurality of heated elements disposed under the wafer support in the body wherein the heat generated from each of the heated elements is transferred to the wafer support a gas line conmected to the wafer support for supplying gas to the plurality of troughs means for supplying heat to the heated elements and a controller connected to the heated elements for controlling the temperature of the heated elements application_number US 22292898 A description reference will now be made in detail to the preferred embodiments of the present invention examples of which are illustrated in the accompanying drawings fig3 shows a plan view of a heater block according to the present invention fig4 shows an enlarged view of part c of fig3 featuring a plurality of troughs formed on the surface of the wafer support 202 fig5 shows a cross sectional view taken along line ii ii u2032 of fig3 and fig6 shows a plan view of a heater block according to the present invention particularly featuring each heated element 206 which is distributed evenly in its location on the wafer support 202 referring to fig3 6 the heater block according to the present invention comprises a body 200 a bellows 216 a gas line 208 a power supply 203 and a temperature controller 201 the wafer support located at the top of body 200 has a plurality of troughs 220 disposed in various directions at the top face thereof also a plurality of the heated elements 206 each wvrapped with a hot wire 204 are provided in the body 200 the heat generated from the heated elements 206 is conducted to the wafer support 202 the bellows 216.