A MFS type field effect transistor includes a semiconductor layer, a PZT system ferroelectric layer formed on the semiconductor layer, a gate electrode formed on the PZT system ferroelectric layer, and an impurity layer composing a source or a drain, formed in the semiconductor layer. The PZT system ferroelectric layer includes Nb that replaces a Ti composition by 2.5 mol % or more but 40 mol % or less.