Broadly tunable, narrowband wavelength filters that can be integrated with other photonic devices are important elements for WDM multi/demultiplexing systems. Recently, we have demonstrated a broadly tunable, narrowband wavelength selective grating assisted vertical directional coupler with a 215 Å tuning range. In the Letter, an improved version of the vertically stacked buried rib InGaAsP/InP integrable wavelength filter that has a tuning range greater than 370 Å is reported.