Patent ID: 8633073

Claim:
A method of forming a semiconductor device, the method comprising: forming a first groove in a semiconductor substrate; forming a first conductive film in the first groove and over the semiconductor substrate; planarizing the first conductive film over the semiconductor substrate; selectively etching the planarized first conductive film to have the planarized first conductive film remain in a lower portion of the first groove; forming a plurality of device isolation grooves in a main surface of the semiconductor substrate; and forming a plurality of device isolation films in the plurality of device isolation grooves to form a plurality of device isolation regions and to define at least one device formation region by the plurality of device isolation regions, wherein forming the first groove comprises forming the first groove which extends to cross the device formation region, wherein planarizing the first conductive film comprises: forming a planarizing film over the first conductive film; and carrying out a first etching process under a condition that an etching rate of the planarization film to an upper portion of the first conductive film is in the range of 0.5to 1.5.