Combined gate cap or digit line and spacer deposition using HDP

A process for forming a silicon nitride or silicon oxide film on a semiconductor substrate, comprising:

• forming vertical surfaces and horizontal surfaces on said substrate, said horizontal surfaces including raised horizontal surfaces above a base plane of said substrate;
• disposing said substrate within a reaction zone of a high density plasma reactor;
• during a first stage of said process, performing the acts of:
• applying a source power to a plasma source in said reactor to generate a high density plasma in said reaction zone,
• introducing a gas mixture containing a silicon compound and at least one other reactant gas capable of reacting with said silicon compound to form either silicon nitride or silicon oxide into said reaction zone, and passing said gas mixture into contact with said substrate while exciting said gas mixture with a high density plasma, and
• biasing said substrate with a bias power to form a layer of silicon dioxide or silicon nitride on said vertical and horizontal surfaces of said substrate;
• and
• during a second stage of said process, continuing to form said layer of silicon dioxide or silicon nitride on said vertical and horizontal surfaces of said substrate, while selectively controlling the thicknesses of said layer of silicon dioxide or silicon nitride film formed on said vertical surfaces and said horizontal surfaces, independently, by changing at least one of said bias power, said source power, and a flow rate of said gas mixture.