In some embodiments of the present invention, the buried silicon oxide technology is employed in the fabrication of fluid channels, particularly nanochannels. For example, a fluid channel can be made in a buried silicon oxide layer by etching the buried oxide layer with a method that selectively removes silicon oxide but not silicon. Thus, one dimension of the resulting fluid channel is limited by the thickness of the buried oxide layer. It is possible to manufacture a very thin buried oxide layer with great precision, thus a nanochannel can be fabricated in a controlled manner. Moreover, in addition to buried oxide, any pairs of substances with a high etch ratio with respect to each other can be used in the same way. Further provided are the fluid channels, apparatuses, devices and systems comprising the fluid channels, and uses thereof.