High manufacturing yield is realized and variation in threshold voltage of each MOS transistor in a CMOS·SRAM is compensated. Body bias voltages are applied to wells for MOS transistors of each SRAM memory cell in any active mode of an information holding operation, a write operation and a read operation of an SRAM. Threshold voltages of PMOS and NMOS transistors of the SRAM are first measured. Control information is programmed into control memories according to results of determination. Levels of the body bias voltages are adjusted based on the programs so that variations in the threshold voltages of the MOS transistors of the CMOS·SRAM are controlled to a predetermined error span. Body bias voltage corresponding to a reverse body bias or an extremely shallow forward body bias is applied to a substrate for the MOS transistors with an operating voltage applied to the source of each MOS transistor.