Objective of the present proposal is to establish the basis of ultra-low-power circuit operation by achieving steep slope of gate voltage for on/off switching through the successful Datta-Das type spin transistor of semiconductor nanowires. Low voltage operation of conventional semiconductor electron device (CMOS integrated circuit) is limited by Boltzmann factor. As a result, modern integrated circuits is confronted with the power consumption problem by the continuing integration level of million gates and operation speed exceeding a few Ghz. It is anticipated that extremely low voltage operation is feasible if spin degree of freedom is used in ferromagnet/semiconductor hybrid structure as will be explained extensively in the description of research projects