ONERA has been developing a Coriolis Vibrating Gyroscope (CVG) named VIG (Vibrating Integrated Gyro). The fabrication process generates structural defects which induce asymetries in the tunning fork geometry. It results in undesirable quadrature error which limitates the performance by increasing sensitivity to phase and temperature variation and causing poor bias stability. This paper deals with the global modelling of the VIG to improve its performances by compensating quadrature error. A full model of the micro-gyroscope is presented, covering mechanical and electrical aspects. The analysis of its performances is focused on mechanical coupling and aims at implementing a solution to improve bias stability by 7 times.