A second mask 320 may be disposed on the first photoresist pattern PR1, and the first photoresist pattern PR1 may be exposed using the second mask 320. The second mask 320 may include a light transmitting portion 321 and a light blocking portion 322. The light transmitting portion 321 may transmit light, and the light blocking portion 322 may block light. The light blocking portion 322 may overlap the first region R1 and the second region R2 of the preliminary polysilicon pattern 136, and the light transmitting portion 321 may overlap the third region R3 of the preliminary polysilicon pattern 136.

The second photoresist pattern PR2 may be formed by developing the first photoresist pattern PR1 irradiated with light through the second mask 320. A portion of the first photoresist pattern PR1 corresponding to the light transmitting portion 321 may be substantially entirely removed, and a portion of the first photoresist pattern PR1 corresponding to the light blocking portion 322 may remain without being substantially removed.

Then, as illustrated in FIG. 11, the preliminary polysilicon pattern 136 may be etched using the second photoresist pattern PR2.

The third region R3 of the preliminary polysilicon pattern 136 exposed by the second photoresist pattern PR2 may be etched by a third thickness TH3 obtained by subtracting the second thickness TH2 from the first thickness TH1 by dry etching, wet etching, or the like. As the third region R3 of the preliminary polysilicon pattern 136 is partially etched, the polysilicon pattern 138 may be formed.