Provided are a lead-free solder, a solder paste, and a semiconductor device, and more particularly, a lead-free solder that includes Cu in a range from about 0.1 wt % to about 0.8 wt %, Pd in a range from about 0.001 wt % to about 0.1 wt %, Al in a range from about 0.001 wt % to about 0.1 wt %, Si in a range from about 0.001 wt % to about 0.1 wt %, and Sn and inevitable impurities as remainder, a solder paste and a semiconductor device including the lead-free solder. The lead-free solder and the solder paste are environment-friendly and have a high high-temperature stability and high reliability.