| 摘要 |
PURPOSE:To improve an operation speed by a method wherein a gate electrode is composed of a plurality of polycrystalline silicon layers and the impurity concentration of the lowermost polycrystalline silicon layer is made to be high and an oxide film is formed over the polycrystalline silicon layers. CONSTITUTION:A gate oxide film 2 is formed on a silicon substrate 1. Then a polycrystalline silicon layer 3 containing a large quantity of phosphorus as impurity is built up and a polycrystalline silicon layer 4 containing a small quantity of phosphorus as impurity is built up on it. Then the layer 3 and the layer 4 are formed in to a required pattern by a photolithography technology to form a gate electrode. An oxide film 5 is formed by a thermal treatment in an oxygen atmosphere. At that time, the thicknesses of oxide films 5a on the side surfaces of the layer 3 are increased and the oxide films 5a are formed under both ends of the layer 4, too. The source and drain regions 6 of a transistor are formed by ion implantation technology and self-alignment technology. If the thickness of the oxide film 5a is controlled, the operation speed can be improved without increase of the parasitic capacitances between the source and drain regions and the gate electrode. |
