Patent ID: 8664079

Claim:
A method for fabricating a semiconductor device, comprising: forming pad oxide layers over a frontside and a backside of a substrate; forming hardmask layers over the pad oxide layers on the frontside and the backside of the substrate; forming sacrificial oxide layers over the hardmask layers on the frontside and the backside of the substrate; removing one of the sacrificial oxide layers over one of the hardmask layers on the frontside of the substrate; performing a chemical mechanical polishing to remove one of the sacrificial oxide layers and a top portion of a dielectric layer on the frontside of the substrate; removing one of the hardmask layers over one of the pad oxide layers on the frontside of the substrate, whereby one of the hardmask layers over one of the pad oxide layers on the backside of the substrate is protected by one of the sacrificial oxide layers on the backside of the substrate; and removing one of the pad oxide layers on the frontside of the substrate and one of the sacrificial oxide layers on the backside of the substrate simultaneously by wet etching.