The first photoresist pattern PR1 may be formed by developing the photoresist layer PRL irradiated with light through the halftone mask 330. A portion of the photoresist layer PRL corresponding to the light transmitting portion 331 may be substantially entirely removed, and a portion of the photoresist layer PRL corresponding to the light blocking portion 332 may remain without being substantially removed. A portion of the photoresist layer PRL corresponding to the light transflective portion 333 may be partially removed. Accordingly, the first photoresist pattern PR1 in which a thickness of the portion corresponding to the light blocking portion 332 is greater than a thickness of the portion corresponding to the light transflective portion 333 may be formed.

Then, as illustrated in FIG. 16, the polysilicon layer 134 may be etched using the first photoresist pattern PR1.

A region other than the first region R1, the second region R2, and the third region R3 of the polysilicon layer 134 exposed by the first photoresist pattern PR1 may be etched by the first thickness TH1. As the region of the polysilicon layer 134 other than the first region R1, the second region R2, and the third region R3 is entirely etched, a preliminary polysilicon pattern 136 may be formed.

Then, as illustrated in FIG. 17, a second photoresist pattern PR2 may be formed by patterning the first photoresist pattern PR1.