A method of manufacturing an IPS-LCD using a 4-mask process including forming amorphous silicon islands and contact holes using the same mask. Each amorphous silicon island is used to form the channel of one transistor inside the active area, and each contact hole is used to form a portion of an anti-ESD circuit around the active area. Amorphous silicon islands and the contact holes are also found using a phase-shaft mask. The phase shift mask at least includes a high transmittance area, a low transmittance area, and a transparent area.