To provide a thin film transistor which does not give influence on a thermally fragile substrate.

In the manufacturing method, a rapid thermal annealing (RTA, local heating) is conducted only to desired spots using a lamp (typically, a halogen lamp) for heat treatment. In addition, the rapid thermal annealing is conducted after a metal layer or an amorphous semiconductor which absorbs heat is provided on the substrate. Accordingly, a semiconductor and a gate insulation film of the thin film transistor are heated up to about 700°C, but the heating temperature of the substrate rises to about 400°C, protecting the substrate from damage. In addition, two treatments of a heat treatment to the gate insulation film and an activation process of an impurity element added to the semiconductor and a gettering process of a metal element added to the semiconductor are simultaneously conducted using the RTA. Since the RTA can be conducted within a short period of time, improvement in the productivity can be expected.