We propose a new monolithic widely tunable semiconductor laser?multi-channel interference (MCI) laser. Multi-arm interference is used for mode selection, which is simple to manufacture and has large tolerance. The wavelength tuning range of the MCI laser based on the electro-optic effect is more than 40 nm, the side mode suppression ratio (SMSR) is more than 40 dB in the whole tuning range, and the fiber output power of the device integrated with the laser and the semiconductor optical amplifier is more than 13 dBm. In the meanwhile, the wavelength tuning range of the MCI laser based on thermo-optical effect is greater than 45 nm, the SMSR is larger than 48 dB, the line width is less than 250 kHz, and the total thermal tuning power consumption is less than 50 mW. In this paper, the theoretical design, fabrication, and test of the device are described in detail.