This paper shows a new design approach that allows to integrate an efficient balun into mm-wave radio frequency integrated circuits (RFIC). The proposed device is an evolution of the simple transformer. Thanks to the modification on the device's shape, the performance increases considerably, maintaining limited dimensions. The proposed balun shows a very good power division with only 0.5 dB of maximum amplitude imbalance within the whole band of interest and less than 10°phase imbalance around 60 GHz. The measurement campaign confirms the accuracy of the electromagnetic simulations and the behaviour of the device. The balun is implemented in ST Microelectronic's 65nm bulk CMOS technology and is employed in a double balanced 60 GHz down-conversion mixer to provide the balanced the LO and RF signal.