Method of forming a via contact

A method of forming a device comprising:

• providing a substrate prepared with a transistor having at least one contact region, wherein the transistor comprises a gate and sidewalls;
• forming a conformal etch stop layer on the substrate, wherein the etch stop layer covers sidewalls of the transistor, a top surface of the gate and substrate;
• forming a contact dielectric layer on the substrate, wherein the contact dielectric layer covers the substrate and etch stop layer;
• and
• forming at least one contact opening through the contact dielectric layer, wherein upper portion of the contact opening includes wider opening with tapered sidewall profile while lower portion of the contact opening includes narrower opening with vertical sidewall profile, wherein forming at least one contact opening comprises:
• providing a patterned mask layer over the contact dielectric layer, wherein the patterned mask layer comprises at least one opening corresponding to the contact region,
• removing portions of the contact dielectric layer exposed by the opening of the mask layer to form the at least one contact opening extending from a top surface to a bottom surface of the contact dielectric layer, the at least one contact opening having an initial vertical sidewall profile throughout its depth from the top surface of the contact dielectric layer, and
• integrating an etch back process with a mask layer removal process, wherein the mask layer removal process removes the patterned mask layer and the etch back process removes upper portion of the contact opening such that the upper portion of the contact opening includes wider opening with tapered sidewall profile.