| 摘要 |
PURPOSE:To enable to further increase the mutual conductance gm by a method wherein the device is formed in a structure wherein a layer having conductivity type reverse to the source and drain and an impurity concentration relatively higher than those of them is opposed to them via a layer of relatively lower impurity concentration having the same conductivity type as this layer. CONSTITUTION:A P type Si substrate 2B, the source 3B and drain 4B composed of poly Si which contains an N type impurity, a thin gate oxide film 5, the gate 6B composed of poly Si which contains the N type impurity, an oxide film 7B used for element isolation, and P type diffused layers 20B for the channel cut of a parasitic MOST are formed as shown in the figure. The areas of the source 3B and drain 4B in contact with the substrate is made as small as possible so as to become sufficient areas to pass a channel current, and the P type diffused layers 20B are placed as close as possible to the range whereby insulation breakdown is not generated between the source 3B and drain 4B. Thereby, the number of impurity atoms of the substrae 2B which are ionized is small, and accordingly the expansion of a depletion layer becomes small. |
