25 will be indicated with the same references as in fig2 to 25 and will not be described in detail this is also true with other embodiments of the present invention which will be described later the first embodiment has one characteristic shown in fig2 b and 2 c for example more particularly each of diffusion layers 16 d and 16 s as source drain regions is designed to have a double structure including an outer middle concentration doped extension region 16 a and diffusion region 16 b and an inner high concentration doped region 16 c as shown in fig2 b further a gate electrode side wall 22 of a nitride film is formed across a gate electrode 7 with a thin oxide film 21 being laid between them the contact plugs 9 d and 9 s are formed with these gate electrode side walls 22 being laid between them this is also true for the sectional view in fig2 c because of the aforementioned semiconductor device construction the life of holes being minority carriers in the high concentration region 16 c is considerably short and thus the bipolar operation does not easily occurs between floating bodies and the n diffusion layer adjacent to one another also data interference will not occur between cells the semiconductor device constructed as above is produced as will be described in due order below with reference to fig4 and 5 fig4 and 5 show sectional views respectively corresponding to fig2 b as shown in fig4 a the semiconductor device includes an soi substrate 100 that is similar to that having previously been described with reference to fig2 b as especially shown in fig2.