A magnetically enhanced radio frequency (13.56 MHz) synchronized triode reactor with a multihole cathode used for etching of Si by a plasma is described. The ion energy is controlled independently of the plasma creation function by adjusting the phase difference between the two rf signals. The cathode shape allows a decreasing of the self-bias potential and an increasing of the ion current density when the plasma is created in the holes. We have studied the effects of ion energy and incident power on etch rate, contaminations and morphology of Si samples. The effects of the magnetic confinement and the electrode shape on the etch rate are also presented. Relative to a standard plate electrode, the etch rate is enhanced by a factor of about three at a pressure of 10 mTorr and a power of 500 W.