Manufacturing method of thin film transistor and semiconductor device utilized for liquid crystal display

摘要

A manufacturing method of a thin film transistor consists of the steps of depositing an active semiconductor layer, a gate insulating layer, and a gate electrode on a transparent glass substrate in that order, forming source and drain regions by doping impurities into the active semiconductor layer according to an ion implantation method while functioning the gate electrode as a mask against the impurities, oxidizing a side portion of the gate electrode according to an anodic oxidation processing to form an anodic oxidation layer made of an insulating material, depositing a layer-insulation layer on the gate electrode and the anodic oxidation layer, and connecting source and drain electrodes to the source and drain regions. A channel region not doped with the impurities is formed in the active semiconductor layer between the source and drain regions, and an off set region positioned just under the anodic oxidation layer is formed in a portion of the channel region adjacent to the drain region. Therefore, an off current flowing from the drain region to the source region is decreased in a backward bias condition because of the off set region, so that a picture signal can be stored in the thin film transistor for a long time.