a method of manufacturing a semiconductor device , in which a stress film having a large stress can be formed with high accuracy over a transistor . the method comprises the steps of : depositing a tensile stress film over the whole surface of a substrate having formed thereon an n - mosfet ; removing by etching the deposited stress film while leaving it on the n - mosfet ; and performing uv irradiation to the remaining stress film . by the uv irradiation , a tensile stress of the stress film is improved . further , although the stress film is cured by the uv irradiation , occurrence of etching defects caused by the curing is prevented because the uv irradiation is performed after the etching . thus , speeding - up and high quality of the n - mosfet can be attained .