The invention discloses a multi-grid 
transistor, which comprises a substrate, an 
oxide layer positioned on the substrate, a fin-shaped structure which is positioned on the 
oxide layer, is connected with the substrate and comprises a trench region and a source region and a drain region which are positioned at two ends of the trench region, a grid 
dielectric layer which is positioned on the fin-shaped structure and wraps the trench region, and a grid which is positioned on the 
oxide layer and the grid 
dielectric layer and is perpendicular to the fin-shaped structure. The multi-grid 
transistor is characterized in that the source region and the drain region consist of 
metal silicate. According to a 
semiconductor device and a manufacturing method thereof, the 
metal silicate is completely used as the source region and the drain region of the fin-shaped structure of the multi-grid 
transistor, so that source and drain serially connected resistance is effectively reduced, and the problem that a non-crystallized region cannot be crystallized after being quenched because of 
doping of a source and a drain is solved; and furthermore, doped 
ion gathering regions are arranged at interfaces between the trench region and the 
metal silicate, so that the 
Schottky barrier height is effectively reduced, and the device performance is improved.