According to an embodiment, the present invention provides a semiconductor device that is easily integrated with other electronic circuits and functions as an oscillator with high frequency accuracy. The semiconductor device includes: a semiconductor substrate; an element region; an element isolation region that surrounds the element region; a field effect transistor including a gate electrode that is formed on the element region, source and drain regions, and a channel region that is interposed between the source region and the drain region; gate, source, and drain terminals that are used to apply a voltage to the gate electrode, the source region, and the drain region, respectively; and an output terminal that is electrically connected to the channel region. When the threshold voltage of the field effect transistor is Vth, a gate voltage Vgs applied between the source terminal and the gate terminal and a drain voltage Vds applied between the source terminal and the drain terminal satisfy the following relationship: Vth