A semiconductor device, comprising: a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type that is formed near a surface of the first semiconductor layer ; a first main electrode that is electrically connected to the second semiconductor layer ; a third semiconductor layer of the second conductivity type that neighbors the first semiconductor layer and is formed near a surface of the first semiconductor layer opposite to the second semiconductor layer ; a fourth semiconductor layer of the first conductivity type that is selectively disposed in an upper portion of the third semiconductor layer ; a second main electrode that is electrically connected to the third semiconductor layer and the fourth semiconductor layer ; a trench whose side face is in contact with the third semiconductor layer and the fourth semiconductor layer , while reaching the first semiconductor layer ; a gate electrode that is formed by a sidewall of polysilicon along the side face of the trench ; and a polysilicon electrode that is disposed away from the gate electrode within the trench and electrically connected to the second main electrode , wherein the polysilicon electrode is electrically connected to the second main electrode through a first contact hole which is discontinuously disposed on the polysilicon electrode , characterized in that at least a part of a first insulator film between the polysilicon electrode and the first semiconductor layer is thicker than a second insulator film between the gate electrode and the first semiconductor layer , and an upper surface of an outer periphery portion of the first insulator film forms a taper surface that lowers toward the gate electrode , and an end face of the polysilicon electrode is disposed on the taper surface. a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type that is formed near a surface of the first semiconductor layer ; a first main electrode that is electrically connected to the second semiconductor layer ; a third semiconductor layer of the second conductivity type that neighbors the first semiconductor layer and is formed near a surface of the first semiconductor layer opposite to the second semiconductor layer ; a fourth semiconductor layer of the first conductivity type that is selectively disposed in an upper portion of the third semiconductor layer ; a second main electrode that is electrically connected to the third semiconductor layer and the fourth semiconductor layer ; a trench whose side face is in contact with the third semiconductor layer and the fourth semiconductor layer , while reaching the first semiconductor layer ; a gate electrode that is formed by a sidewall of polysilicon along the side face of the trench ; and a polysilicon electrode that is disposed away from the gate electrode within the trench and electrically connected to the second main electrode , wherein the polysilicon electrode is electrically connected to the second main electrode through a first contact hole which is discontinuously disposed on the polysilicon electrode , characterized in that at least a part of a first insulator film between the polysilicon electrode and the first semiconductor layer is thicker than a second insulator film between the gate electrode and the first semiconductor layer , and an upper surface of an outer periphery portion of the first insulator film forms a taper surface that lowers toward the gate electrode , and an end face of the polysilicon electrode is disposed on the taper surface. <EOS>