Manufacturing method and semiconductor device

Abstract

A semiconductor device manufacturing method includes: forming a first groove having depth H in a semiconductor layer; filling the first groove with an oxide film and forming a surface oxide film having thickness a on an upper surface of the semiconductor layer to equalize the oxide film and the surface oxide film in height; forming a second groove having depth h greater than thickness a, from an uppermost surface of a third oxide film; forming gate trenches deeper than depth H, in the semiconductor layer; depositing polysilicon until at least the gate trenches and the second groove are filled with polysilicon; forming a peripheral element by injecting an impurity into polysilicon deposited in the second groove; and making a thickness of the peripheral element equal to depth h by concurrently removing polysilicon deposited in the gate trenches and polysilicon deposited in the second groove until they become equal in height.