| 摘要 |
PURPOSE:To reduce the minimum required operation voltage for a SRAM by a method wherein the formation part of word transistors in a p type well region is ion-implanted with n type impurities so that the peak position of the implanted ion concentration may be located at the specific distance from the surface of the well region. CONSTITUTION:An opening is made only in the word transistors Q3 and Q4 of a memory cell part encircled by an interelement separation insulating layer 3 while the other part especially the formation part of driver transistors Q1 and Q2 is covered with the photoresist to be an ion-implantation mask and then n type impurities P<+> or As<+> are ion-implanted using the interlayer separation insulating layer 3 as a mask to form an ion-implanted region 15A so that the peak position of the impurities may be located at the specific distance from the surface side not limited to the formation part of the word transistors in the well region 2. Next, when the implanted impurities are activated and diffused by the later heat treatment, the concentration of the p type impurities extending over the surface from the inside of the well region 2 can be offset by the n type impurities due to the ion-implantation thereby enabling the Vccmin to be reduced by lowering the concentration. |
