Method and apparatus for removing a photoresist layer from a substrate surface of different material, such as a semiconductor slice, in the fabrication of an electronic structure, involving exposure of the photoresist layer to an ozone-containing gaseous atmosphere in a reaction zone of a reactor. The ozone is present as an active reagent in the gaseous atmosphere to which the layer of photoresist material is exposed in an amount sufficient to react with all of the photoresist material in the layer thereof, with the photoresist material being removed from the underlying substrate surface in response to its exposure to the ozone. The photoresist material being treated by the ozone for stripping thereof may be either a negative or positive photoresist. Gaseous reaction products resulting from treatment of the substrate and removal of the photoresist layer therefrom are directed through an ozone reduction chamber prior to the discharge of the exhaust gases created by the reaction of the ozone with the photoresist material, wherein any excess ozone contained in the exhaust gases is reduced to molecular oxygen.