A thin film transistor substrate structure of a horizontal electric field type LCD comprises a plurality of signal lines including a gate, a data, and a common lines disposed on a substrate; the data line intersecting with the gate and common lines, a gate insulating film disposed between the data line and the gate and common lines, a pixel area being defined by the intersection of the data and gate lines; a thin film transistor disposed at the intersection of the data line and gate line; a common and a pixel electrodes both having a portion extended into the pixel area; a protective film disposed over the substrate and the thin film transistor; and at least one pad structure including an upper pad electrode contacting a lower pad electrode within a first contact hole wherein the upper pad electrode is absent from the upper surface of the protective film.