The invention encompasses a method of forming a silicon nitride layer. A substrate is provided which comprises a first mass and a second mass. The first mass comprises silicon and the second mass comprises silicon oxide. A sacrificial layer is formed over the first mass. While the sacrificial layer is over the first mass, a nitrogen-containing material is formed across the second mass. After the nitrogen-containing material is formed, the sacrificial layer is removed. Subsequently, a silicon nitride layer is formed to extend across the first and second masses, with the silicon nitride layer being over the nitrogen-containing material. Also, a conductivity-enhancing dopant is provided within the first mass. The invention also pertains to methods of forming capacitor constructions.