Piezoresistive detection resonant device comprising a substrate, a mobile par configured to move with respect the substrate, suspension elements suspending the mobile part to the substrate, a piezoresistive detection device to detect the motions of the mobile part, said piezoresistive detection device comprising at least one strain gauge, wherein the piezoresistive detection resonant device also comprises a folded spring with at least two spring arms, connected to the mobile part and configured to be deformed by the motion of the mobile part, the at least one gauge being suspended between the substrate and the folded spring in such manner that the deformation of the gauge is reduced compared to the motion of the mobile part.