A semiconductor processing apparatus is described that has a body with a wall defining two processing chambers within the body; a passage through the wall forming a fluid coupling between the two processing chambers; a lid removably coupled to the body, the lid having a portal in fluid communication with the passage; a gas activator coupled to the lid outside the processing chambers, the gas activator having an outlet in fluid communication with the portal of the lid; a substrate support disposed in each processing chamber, each substrate support having at least two heating zones, each with an embedded heating element; a gas distributor coupled to the lid facing each substrate support; and a thermal control member coupled to the lid at an edge of each gas distributor.