A 1.5 µm semiconductor wavelength tunable optical filter using a λ/4-shifted passive waveguide grating resonator has been developed. Both wavelength channel number and transmissivity are analyzed with respect to grating coupling coefficient, filter length, and waveguide loss. The influence of facet reflectivity and phase-shift value on transmissivity and wavelength channel number are also investigated. A wavelength shift as wide as 42 Å is able to be obtained by carrier injection with the fabricated filter.