Patent ID: 7132317

Claim:
A method of manufacturing a semiconductor device, comprising: forming a first semiconductor film and a second semiconductor film on an insulating surface; forming an insulating film over the first and second semiconductor films; forming a first conductive film over the first semiconductor film and a second conductive film over the second semiconductor film; performing a first heat treatment after forming the first and second conductive films; introducing a first impurity element into the first and second conductive films and the first and second semiconductor films; introducing a second impurity element into the second conductive film and the second semiconductor film performing a second heat treatment to change internal stresses in the first conductive film and in the second conductive film, and making a stress that the first semiconductor film receives a tensile stress and making a stress that the second semiconductor film receives a compressive stress; and manufacturing an n-channel TFT by using the first semiconductor film, the insulating film and the first conductive film and manufacturing a p-channel TFT by using the second semiconductor film, the insulating film and the second conductive film, wherein the first conductive film constitutes a gate electrode of the n-channel TFT, and wherein the second conductive film constitutes a gate electrode of the p-channel TFT.