| 摘要 |
PURPOSE:To reduce a threshold voltage of a semiconductor element by forming an impurity-undoped polycrystalline silicon film, and then heat treating it at high temperature to reduce the thickness of a gate oxide film. CONSTITUTION:With a patterned first polycrystalline silicon film 17 as a mask boron of P-type impurity is doped by implanting, and heat treated at 1200 deg.C, for example, in an N2 atmosphere so that the depth of the junction of a P<-> type layer 18 becomes 3-4mum or more. Then, after photolithography, an N type impurity is doped by implanting to form N<+> type layer 19 of source, drain, and a P-type impurity is doped by implanting after a normal photolithography to form a P<+> type layer 20 of the contact output of the layer 18. Then, a second polycrystalline silicon film 21 is so formed on the whole surface as to contact directly on the film 17, and an N-type impurity is diffused, for example, by a diffusing method in high density on the whole surface. The film 20 is then so patterned in a photolithoetching step to cover the first polycrystalline silicon film. |
