the present invention relates to an oscillator having a first substrate on which a resonator circuit and an amplifier circuit are arranged . the resonator circuit has a first set of components and the amplifier circuit has an amplifier transistor and a second set of components . the first substrate includes at least two additional substrates : a second substantially insulating substrate and a third substantially semiconducting substrate . at least the amplifier transistor is arranged on the third substrate and the first and second sets of components are arranged on the second substantially insulating substrate .