Method for manufacturing semiconductor devices

Abstract

The method for manufacturing semiconductor devices, according to the present invention, that include transistors for peripheral circuits to which input and output signal lines are connected and transistors for internal circuits that have lower operation voltage than that of the transistors for peripheral circuits consists of the steps of exposing a surface of a first region forming the transistors for peripheral circuits of a semiconductor substrate, forming a first gate oxide layer by oxidizing the exposed surface of the first region in an oxidizing atmospheric gas including hydrogen atoms, exposing a surface of a second region forming the transistors for internal circuits of the semiconductor substrate, and forming a second gate oxide layer by oxidizing the exposed surface of the second region in an oxidizing atmospheric gas without hydrogen atoms and subsequently by oxidizing the exposed surface in a nitrogen monoxide atmosphere.

Dependencies are inferred from the claim text.