| 摘要 |
PURPOSE:To obtain an IC having an FET, with different threshold voltage on the same substrate with a MISFET of diffusion self-adjusting type whose impurity concentration of effective channel and length are different from each other. CONSTITUTION:A p<+>-layer 19 is prepared by protecting a drain D on a p-type Si base board 1 with a resist 18, injecting B ion into a source S and heat-treating in an N2. At this time, if amount of the injection is changed, changes are brought about to diffusion depth of the layer 19, diffusion length in the direction of channel and the base board surface concentration. After removal of the resist and cleaning, the base board is exposed to phosphorous atmosphere to prepare a source 22 and a drain 23. At this time, a difference 21 in lateral diffusion length between the p<+>-layer 19 and the source 22 becomes an effective channel. And then, electrodes 24 through 26 are attached as prescribed. By doing so, it is possible to prepare an IC, which has FETs of a variety of diffusion self-adjustment structures of different threshold values in the same base board, simply by changing amount of injection of impurities at the time when the p<+>-layer is formed. |
