To provide a semiconductor device capable of preventing defects due to etching such as an increase in leakage current, a deterioration in coating properties, and a deterioration in transistor characteristics, and to provide a method of manufacturing the same.

A CMOS transistor 500 includes an N-type MOS transistor having a gate electrode 202 and a P-type MOS transistor having a gate electrode 201 on the same semiconductor substrate 1. The gate electrode 202 includes a gate insulating film 5, a polycrystalline silicon layer 61, a metal layer 62, and a polycrystalline silicon layer 63. The gate electrode 201 includes the gate insulating film 5, the metal layer 62, and the polycrystalline silicon layer 63.