US Patent 7573069 Semiconductor device and manufacturing method thereof

A semiconductor device having high operating performance and reliability, and a manufacturing method thereof are provided. An LDD region 207 provided in an n-channel TFT 302 forming a driving circuit enhances the tolerance for hot carrier injection. LDD regions 217-220 provided in an n-channel TFT (pixel TFT) 304 forming a pixel portion greatly contribute to the decrease in the OFF current value. Here, the LDD region of the n-channel TFF of the driving circuit is formed such that the concentration of the n-type impurity element becomes higher as the distance from an adjoining drain region decreases.