An exemplary method of heating an amorphous semiconductor film formed in the recess in the surface of a wafer W without crystallizing the film by the laser annealing apparatus 100 will be described. First, a wafer W having an amorphous semiconductor film embedded in a recess is placed on the stage 103. Subsequently, the controller 104 controls the operations of the laser light source 101, the laser optical system 102, and the stage 103 so as to execute the heating step described above. In this manner, it is possible to remove a seam in the recess without crystallizing the amorphous silicon film embedded in the recess.

An example performed to confirm the effect of the method of filling a recess according to an embodiment will be described. In the example, after the amorphous silicon film was embedded in a recess using the vertical heat treatment apparatus 1, the laser annealing step was performed on the amorphous silicon film in the recess using the laser annealing apparatus 100.

FIGS. 5A and 5B are views illustrating exemplary results before and after the laser annealing treatment. FIG. 5A illustrates the result before performing the laser annealing step, and FIG. 5B shows the result after performing the laser annealing step. The conditions for the laser annealing treatment are as follows.

<Conditions for Laser Annealing Treatment>

Laser wavelength: 1070 nm

Laser output: 43 W

Sweep speed: 5 mm/sec

Substrate temperature: 800 degrees C.