To provide a display device having a thin film transistor with high electric characteristics and excellent reliability and a manufacturing method thereof. A gate electrode, a gate insulating film provided over the gate electrode, a first semiconductor layer provided over the gate insulating film and having a microcrystalline semiconductor, a second semiconductor layer provided over the first semiconductor layer and having an amorphous semiconductor, and a source region and a drain region provided over the second semiconductor layer are provided. The first semiconductor layer has high crystallinity than the second semiconductor layer. The second semiconductor layer includes an impurity region having a conductivity type different from a conductivity type of the source region and the drain region between the source region and the drain region.