Fabrication method for a thin film semiconductor device, the thin film semiconductor device itself, liquid crystal display, and electronic device

A thin film semiconductor device, comprising.

• a glass substrate of 300 mm×300 mm or more;
• an underlevel protection layer comprising an insulating material, the underlevel protection layer being formed on at least a portion of the substrate;
• and
• a field effect transistor having:
• three silicon oxide semiconductor films formed as said underlevel protection layer,
• a gate insulator layer formed on the semiconductor film,
• a gate electrode formed on the gate insulator layer;
• and
• an electrically insulating interlevel insulator layer formed over the gate electrode and between interconnects of said field effect transistor, the thin film semiconductor device having a thickness that is a sum of thicknesses of the underlevel protection layer, the gate insulator layer, and the interlevel insulator layer, and the thickness of the thin film semiconductor device being about 2 μm or less.