The stabilization of neoclassical tearing modes by phased electron cyclotron current drive (ECCD) and electron cyclotron resonance heating (ECRH) is studied numerically. The dependence of the saturated magnetic island width on the magnitude, width and location of the driven current and the corresponding resistivity perturbation are investigated. Since the saturated island size cannot become much smaller than the width of the driven current layer, this width is one of the most important parameters. Assuming usual heat transport coefficients, the stabilization by ECRH is found to be more effective than that by ECCD for a large island in a middle-size tokamak, while the stabilization by ECCD should be more effective for a tokamak reactor.