The　quasineutral　limit　of　drift-diffusion　models　for　semiconductors　with　PN-junctions　(i.e.　with　a　fixed　bipolar　background　charge)　is　studied　in　the　multi-dimensional　case.　For　generally　smooth　sign-changing　doping　profiles　with　good　boundary　conditions,　the　quasineutral　limit　(zero-Debye-length　limit)　is　justified　rigorously　in　the　Sobolev＇s　norm　uniformly　in　time.　The　proof　is　based　on　the　elaborate　energy　method　and　the　relative　entropy　functional　method　which　yield　the　uniform　estimates　with　respect　to　the　scaled　Debye　length.