A Large-scale integrated thermoelectric (LSI-TE) de-vice was developed in standard Si-CMOS process technol-ogy. The LSI-TE device consists of up to 70 668 stages of silicon-nanowire (Si-NW) thermoelements. Since the TE power of the device element increases by shortening the Si-NWs, the total power capacitance generated from a unit area is improved by miniaturizing each device and increasing the scale of integration. The LSI-TE can be uti-lized also as a heat flux sensor, and it achieved the best record of the heat flux sensitivity.