An oscillator includes a resonator element; and a semiconductor device including an oscillation circuit which outputs an oscillation signal by oscillating the resonator element, a temperature compensation circuit which compensates for temperature characteristics of a frequency of the oscillation signal, and a first surface in which a terminal that is electrically connected to the resonator element is disposed. The semiconductor device overlaps the resonator element in a planar view. Frequency deviation of the oscillation signal, which is compensated for by the temperature compensation circuit, is greater than or equal to −150 ppb and smaller than or equal to +150 ppb in a temperature range from −5° C. to +85° C.