An etch-stop layer is selectively provided between layers of a multiple-layered circuit in a selective manner so as to allow for outgassing of impurities during subsequent fabrication processes. The etch-stop layer is formed over an underlying stud so as to serve as an alignment target during formation...http://www.google.de/patents/US6787906?utm_source=gb-gplus-sharePatent US6787906 - Bit line pad and borderless contact on bit line stud with localized etch stop layer formed in an undermined region
