In one embodiment, a chip-scale LiDAR device can include a chip with three layers. The first layer includes a number of micromechanical system (MEMS) mirrors. The second layer includes a laser source; a beam splitter connected to the laser source; a number of waveguides, each connected to the beam splitter; and a number of beam deflectors, each beam deflector coupled with one of the number of waveguides. The third layer includes a receiving unit for receiving and processing reflected laser signals of one or more laser beams from the laser source. The first layer, the second layer, and the third layer are vertically attached to each other using either wafer bonding and/or solder bonding.