Patent ID: 7238582

Claim:
A process of producing a semiconductor device, comprising the steps of: forming a first polycrystalline silicon layer above a substrate; and forming a second polycrystalline silicon layer, wherein a lower surface of the second polycrystalline silicon layer is in contact with an upper surface of the first polycrystalline silicon layer, and the second polycrystalline silicon layer is thicker than the first polycrystalline silicon layer, wherein the second polycrystalline silicon layer is in electrical connection with the first polycrystalline silicon layer and is adapted to be charged with substantially a same voltage as that of the first polycrystalline silicon layer, wherein crystal grains of the first and second polycrystalline silicon layers have different grain sizes, and wherein a temperature dependence of resistance of said first polycrystalline silicon layer is different from that of said second polycrystalline silicon layer.