A semiconductor device with first and second groups of transistors, the second group transistors each having a lower operating voltage than that of each of said transistors in said first group, the first group transistors have first gate electrodes formed from a silicon based material layer on a semiconductor substrate through a first gate insulating film, the second group transistors have second gate electrodes formed such that metal based gate materials are respectively filled in gate formation trenches formed in an interlayer insulating film on the semiconductor substrate through a second gate insulating film, and a resistor on the substrate has a resistor main body utilizing the silicon based material layer and is formed on the substrate through an insulating film.