Abstract: An apparatus for producing semiconductor devices in which a plurality of treatment chambers such as a load chamber, an etching chamber, a sputtering chamber, an ion implantation chamber, a CVD chamber, an unload chamber, a transfer chamber, a heat-treatment chamber, a rinsing chamber and the like, are connected in series preferably in the form of U for effecting various treatments of semiconductor wafers. Wafer conveyor and transfer means are provided to move a wafer through the treatment chambers in which the wafer is normally sequentially processed and these conveyor and transfer means are reversible so that a wafer which has been moved into a predetermined treatment chamber can be returned to the inlet of the apparatus, whereby the quantity of dust attached to the wafer in each treatment chamber can be easily and positively detected.