An active matrix substrate comprises an insulation substrate, a plurality of pixel electrodes arranged in a matrix form on the insulation substrate, a switching element provided for each of the pixel electrodes, gate signal lines for supplying a signal to the switching elements, and source signal lines for supplying a data signal to the pixel electrodes via the corresponding switching elements. Each switching element is a thin film transistor (TFT) including a gate electrode, an insulating layer formed on the insulation substrate to cover the gate electrode, a semiconductor layer formed on the insulating layer opposite to the gate electrode, a source electrode formed on one end of the semiconductor layer, one of the source signal lines overlapping the source electrode, and a drain electrode formed on the other end of the semiconductor layer, one of the gate signal lines overlapping the drain electrode. The source and drain electrodes have a two-layer structure of an upper amorphous semiconductor layer and a lower micro-crystalline semiconductor layer. The source signal lines have a two-layer structure of an upper conductive layer and a lower protection layer.