SILICON THIN FILM TRANSISTOR

PURPOSE:To reduce the manufacturing cost by composing the active layer of polycrystalline silicon layer and the source-drain regions of polycrystalline germanium layer. CONSTITUTION:A polycrystalline silicon film 2 is deposited on a glass substrate 1. The next step is to deposit a polycrystalline germanium film 3 on the deposited polycrystalline silicon film 2 and to open a channel zone A by etching this polycrystalline germanium film 3. A further step is to anneal this substrate at low temperature to form an alloy layer 2' at the boundary of the polycrystalline silicon film 2 and the polycrystalline germanium film 3. After an SiO2 film is formed on the entire surface of the substrate to form a polycrystalline silicon film, it is selectively removed to form gate electrodes 5 composed of a gate oxide film 4 and polycrystalline silicon. An indium layer 10 is evaporated on the whole substrate and heated to turn the polycrystalline germanium layer 3 into a P type region 3'. An SiO2 film 6 is deposited by CVD info the interlayer insulating film and opened for contact windows, and then Al wiring layers 7 are formed and coated with a passivation film 8. This process allows the manufacture of the title device on a glass substrate at a low temperature process without ion implantation.