In some embodiments a method comprises depositing a first silicon nitride layer on a top surface of a semiconductor wafer and forming one or more first gaps in the first silicon nitride layer. The one or more first gaps can relieve stress formed in the first silicon nitride layer. A first fill material is deposited on the first silicon nitride layer and the first silicon nitride layer is planarized. A second silicon nitride layer is deposited across the first silicon nitride layer and one or more second gaps are formed in the second silicon nitride layer. The one or more second gaps can relieve stress formed in the second silicon nitride layer. A second fill material is deposited across the second silicon nitride layer and the second silicon nitride layer is planarized.