Semiconductor device with liner structure and method for fabricating the same

A method for fabricating a semiconductor device, comprising:

• providing a substrate;
• forming a contact over the substrate;
• forming a bit line over the substrate;
• forming a liner structure enclosing an air gap, wherein the liner structure is formed between the contact and the bit line;
• and
• forming a landing pad over the contact, comprising:
• forming a barrier layer;
• forming a plug in contact with the contact;
• forming a first spacer and a second spacer over the plug,
• forming a first insulating film over the substrate;
• forming a second insulating film over the first insulating film;
• and
• forming a third insulating film over the second insulating film, wherein the bit line is formed in the third insulating film;
• wherein the first spacer is disposed over the plug, and the second spacer sandwiches a protruding portion of the plug;
• wherein forming the liner structure comprises:
• forming a third opening penetrating through the third insulating film and the second insulating film;
• depositing a dielectric layer in the third opening and over the contact, wherein the third opening is partially filled with the dielectric layer so as to form the air gap enclosed by the dielectric layer;
• and
• partially removing the dielectric layer to form the liner structure.