It is an object of an invention disclosed in the present specification to provide a transistor having low contact resistance. In the transistor, a semiconductor film including an impurity element imparting P-type or N-type conductivity, an insulating film formed thereover, and an electrode or a wiring that is electrically connected to the semiconductor film through a contact hole formed at least in the insulating film are included; the semiconductor film has a first range of a concentration of the impurity element (1×1020/cm3 or less) that is included in a deeper region than predetermined depth, and a second range of a concentration of the impurity element (more than 1×1020/cm3) that is included in a shallower region than the predetermined depth; and a deeper region than a portion in contact with the electrode or the wiring in the semiconductor film is in the first range of the concentration of the impurity element.