Contact filling method

A contact filling method, at least comprising:

• step I, providing a first oxide layer, wherein a Co layer embedded in the first oxide layer is formed on one side of the first oxide layer, and the Co layer penetrates through upper and lower surfaces of the first oxide layer;
• forming a stack layer on upper surfaces of the first oxide layer and the Co layer, wherein the stack layer comprises a first SiN layer, a TiN layer, and a second SiN layer in sequence from bottom to top;
• step II, removing the second SiN layer and the TiN layer above the first oxide layer on one side provided with the Co layer by etching, and then covering, with the second oxide layer, the second SiN layer above the first oxide layer on one side provided with no Co layer and the first SiN layer on the side of the first oxide layer that is provided with the Co layer;
• step III, removing the second oxide layer and the second SiN layer above the first oxide layer on the side provided with no Co layer by development etching, until an upper surface of the TiN layer is exposed, so as to form a first contact, wherein the TiN layer acts as the bottom of the first contact, and the diameter of the first contact is less than the width of the first oxide layer;
• step IV, removing the second oxide layer and first SiN layer above the first oxide layer on the side provided with the Co layer by development etching, until the upper surface of the Co layer is exposed, so as to form a second contact, wherein the diameter of the second contact is less than the width of the Co layer;
• step V, forming a selective Co layer on the TiN layer at the bottom of the first contact and on the Co layer at the bottom of the second contact respectively;
• and
• step VI, filling the first contact and the second contact with tungsten respectively.