| 摘要 |
PURPOSE:To obtain a semiconductor device of double structure only at a drain side having small variation of Vth and high mutual conductance gm in simple steps by forming a low density impurity region only at the drain side by utilizing an insulating film containing an impurity. CONSTITUTION:After an insulating film 2 containing an impurity is formed, an insulating film 3 is formed on a semiconductor substrate 1 to cover it with them. A gate electrode layer 4 is formed across the end 2A of the film 2 containing the impurity. After a resist layer 5 is patterned, with the layer 5 as a mask the layer 5, the film 3 and the film 2 are patterned. The layer 5 is removed, a thinner insulating film 7 is formed, and an ion implantation for forming high density impurity regions 6D, 6S is performed. When heat-treated, a low density impurity region 8D is formed by the film 2 only at a drain side, hot electrons are suppressed, Vth is stabilized, a decrease in a mutual conductance gm is prevented to improve element characteristics.
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