Using a RF cylindrical magnetron operated with two electromagnets having a Helmholz configuration, RF magnetron plasma properties and characteristics of reactive ion ething of Si were investigated as a function of applied magnetic field strengths using 3mTorr $CF_4/H_2$ and $CHF_3$. Also, I-V characteristics of Schottky diodes, which were made of silicons etched under different applied magnetic field strengths and gas environments, were measured to investigate the degree of radiation damage during the reactive ion etching. As the magnetic field strent;th increased, ion densities and radical densities of the plasmas were increased linearly, however, the dc self-bias voltages induced on the powered electrode, where the specimen are located, were decreased exponentially. Maximum etch rates, which were 5 times faster than that etched without applied magnetic filed, were obtained using near lOOGauss, and, under these conditions, little or no radiation damages on the etched silicons were found.