A thin film transistor includes a substrate and an active layer formed on the substrate. The active layer includes a channel region, a source region and a drain region. A source electrode and a drain electrode are formed on the source region and the drain region respectively. A gate insulating layer is formed between a gate electrode and the channel region. The thin film transistor further includes a nitride conductive layer formed between the drain electrode and the drain region, and between the source electrode and source region. The nitride conductive layer has a carrier concentration higher than that of the active layer, thereby reducing contacting resistances between the drain electrode and the drain region and between the source electrode and source region.