Channel configurable optical filters are realized by using buried heterostructure semiconductor ring resonators. Two rings having slightly different radii are laterally coupled to bus waveguides in a cascaded manner, which affords free spectral range (FSR) expansion and channel configuration by Vernier effects. The effective FSR and spectral linewidth at resonance measured from a drop port are 10.2 and 0.017 nm, respectively, that corresponds to a finesse (F) of 600. By shifting the resonant wavelength of one of the resonators with free carrier injection, we demonstrate digital tuning filters where a distinct channel isolation of 15-20 dB is achieved with 0.68-nm spectral spacing.