To provide a temperature-compensated crystal oscillator which reduces the height of a product.

The temperature-compensated crystal oscillator 40 comprises a first substrate structure 41 composed of at least one substrate with a cavity formed therein, a second substrate structure 42 composed of at least one substrate disposed on the upside of the first structure 41 with a cavity formed in a region not overlying the cavity of the first structure 41, an IC chip 47 mounted in the cavity of the first structure 41, a crystal oscillator piece 43 mounted in the cavity of the second structure 42, a resin 49 formed by filling the cavity containing the IC chip 47 with resin to form a substantially planarized surface on the downside of the first structure 41, and a metal cover 45 disposed on the upside of the second structure 42 to cover the cavity of the second structure 42.