Bonding method for flip-chip semiconductor device, mems device package and package method using the same

A side-bonding method of a flip-chip semiconductor device, a MEMS device package and a package method using the same, in which firm bonding and insensitivity to surface roughness may be obtained, include forming a UBM on a bonding line of a lower substrate having a semiconductor device formed thereon, plating solder on the UBM on the lower substrate, forming a trench in the upper substrate to contact the lower substrate at a location corresponding to a location of the solder and forming a second UBM in the trench, coupling the upper substrate and the lower substrate by inserting the solder into the trench, and heating the upper substrate and the lower substrate at a temperature higher than a melting point of the solder so that the solder is wetted toward sides of the trench to bond the upper substrate and the lower substrate.