A heat treatment apparatus for use in batch heating/wafer processing is provided, which comprises a process chamber for receiving a wafer boat, at least a heating element comprising a substrate body configured to form an electrical heating circuit for at least one heating zone and encapsulated in a continuous overcoat layer, a heat reflector comprising a heat reflective surface disposed on the heating element, and the heating element has a ramp rate of at least 1.degree. C. per second for heating the wafers in the wafer boat.