For　circuit　designs　in　advanced　technologies,　standard-cell　libraries　consist　of　cells　with　different　heights;　for　example,　the　number　of　fins　determines　the　height　of　cells　in　the　Fin　FET　technology.　Cells　of　larger　heights　give　higher　drive　strengths,　but　consume　larger　areas　and　power.　Such　mixed　cell　heights　incur　new,　complicated　challenges　for　layout　designs,　due　mainly　to　the　heterogeneity　in　cell　dimensions　and　thus　their　larger　solution　spaces.　There　is　not　much　published　work　on　layout　designs　with　mixed-height　standard　cells.　This　paper　addresses　the　legalization　problem　of　mixed-height　standard　cells,　which　intends　to　place　cells　without　any　overlap　and　with　minimized　displacement.　We　first　study　the　properties　of　Abacus,　generally　considered　the　best　legalization　method　for　traditional　single-row-height　standard　cells　but　criticized　not　suitable　for　handling　the　new　challenge,　analyze　the　capability　and　insufficiencies　of　Abacus　for　tackling　the　new　problem,　and　remedy　Abacuss　insufficiencies　and　extend　its　advantages　to　develop　an　effective　and　efficient　algorithm　for　the　addressed　problem.　For　example,　dead　spaces　become　a　critical　issue　in　mixed-cell-height　legalization,　which　cannot　be　handled　well　with　an　Abacus　variant　alone.　We　thus　derive　a　dead-space-aware　objective　function　and　an　optimization　scheme　to　handle　this　issue.　Experimental　results　show　that　our　algorithm　can　achieve　the　best　wirelength　among　all　published　methods　in　reasonable　running　time,　e.g.,　about　50%　smaller　wirelength　increase　than　a　state-of-the-art　work.　©　2017　IEEE.