As indicated below in Table 1, the S value that indicates the sub-threshold characteristics is unique in that only the S value of complete depletion type SOI transistors is the low value of 60 - 70 mV/dec. (The S value is the gate voltage at the sub-threshold area that changes the drain current by one digit with the drain voltage held constant.) Also, as illustrated in Figure 1, the source, drain, substrate, and the PN junction formed between wells in bulk transistors do not exist as complete depletion type transistors. Also, the junction capacity is very small. Since a PN junction exists at the bottom of the body in partial depletion type transistors, it is located exactly between them. The advantages of the S value, reduced junction capacitance, and the totally isolated structure are as follows.