Semiconductor device and method for manufacturing semiconductor device

摘要

In a method for forming a semiconductor device, the major surface of a substrate is separated into a first element region for forming a first field-effect transistor and a second element region for forming a second field-effect transistor. A silicon nitride film is formed in each of the first and second element regions. Thereafter, the silicon nitride film formed in the second element region is removed, and the substrate is subjected to heat treatment in an ambient that contains nitrogen oxide. Thereby, the silicon nitride film in the first element region is oxidized to form an oxynitride film, and a silicon oxynitride film is formed in the second element region. Thereafter, a high-dielectric-constant film is formed on the silicon oxynitride films in each of the first and second element regions.