Method of forming contact hole and method of fabricating semiconductor device

A method of fabricating a semiconductor device, comprising:

• providing a substrate, a plurality of device structures being formed over the substrate, a first dielectric layer and a conductive layer sequentially covering the device structures and a surface of the substrate, a plurality of first doped regions being formed at the bottom of the device structures, the conductive layer comprising a recess between every two neighboring device structures;
• forming a pair of composite spacers in the recess, the composite spacers comprising a spacer material layer and a spacer protection layer disposed over the spacer material layer, an etching selectivity of the conductive layer to the spacer protection layer being larger than an etching selectivity of the conductive layer to the spacer material layer;
• removing a portion of the conductive layer by using the composite spacers as a mask to form a plurality of openings to expose the substrate in the conductive layer between the neighboring device structures;
• forming a plurality of second doped regions in the substrate at the bottom of the openings;
• forming a second dielectric layer on sidewalls of the openings;
• forming a third dielectric layer over the substrate, the third dielectric layer covering the device structures and the conductive layer;
• removing a portion of the third dielectric layer and the first dielectric layer above the openings to form a plurality of self-aligned contact holes;
• and
• forming a plurality of conductive plugs in the self-aligned contact holes.