Abstarct: Dielectric elastomer resonators (DERs) are applied in a wide variety of applications for micro electro-mechanical systems (MEMSs). In this study, vibrations and bifurcation of a DERs consist of a clamped-clamped sandwiched micro-beam with three elastic and hyper-elastic laxyers grounded by geometric and material nonlinearities is studied. Material nonlinearity modeled with the Yeoh hyper-elastic material theory. The governing equation of motion is formulated by means of Hamilton’s principle and then truncated into a reduced-order model through Galerkin’s technique. Approximate analytical solution in the primary resonant case is obtained using multiple time scale (MTS) method. The stabilities of steady-state responses in the vicinity of the equilibrium states and critical (pull-in) voltages are analyzed. Moreover, bifurcation phenomena is studied considering constant values of DC voltage, different values of frequency detuning parameters, and force excitation as control parameters. The obtained results are validated using results of previous studies and can help us better understand to design of DERs.