The 4004 was the first random logic circuit integrated in one chip using the MOS (metal–oxide–semiconductor) silicon gate technology (SGT). It was the most advanced integrated circuit (IC) design undertaken up until then. Hoff, head of Intel's Application Research department, had formulated an architectural proposal consisting of a block architecture with an instruction set during 1969, while talking with Busicom engineers led by Shima and with the assistance of Stan Mazor. Hoff and Mazor were not MOS chip designers and did not participate in the actual design or development of the 4004.