Because single-stranded DNA (ssDNA) molecules in solution typically form coiled structures, stretching ssDNA is extremely crucial when applying any nanotechnology for ssDNA analysis. Recent advances in material fabrication enable the deployment of nanochannels to manipulate, stretch, sort and map double-stranded DNA (dsDNA) molecules, however nanochannels fail to stretch ssDNA molecules due to the ultra-short persistence length and the potential nonspecific-interaction-induced clogging. Given the significance of ssDNA stretching in genome analysis, here a novel ssDNA stretching platform is proposed: two dimensional in-plane heterostructure comprising graphene and hexagonal boron nitride (h-BN), and I show that ssDNA can be stretched on a h-BN nanostripe sandwiched between two adjacent graphene domains ("nanochannel''). Additionally, with a biasing voltage the stretched ssDNA can be electrophoretically transported along the ``nanochannel'', allowing easy controls/manipulations. When being conveniently integrated with existing atomic resolution sensors, the heterostructure platform paves the way for sequencing DNA on a planar surface [see Nat. Commun. 10, 4610 (2019)].