Two methods for producing Si-oxide barriers upon which crystalline Si layers can be grown are presented. One method entails oxide island nucleation on a clean vicinal Si(001) surface. The second method makes use of void formation in ultrathin oxides on the Si(100) surface at elevated temperatures. Either method results in an oxide barrier which is porous and the exposed Si within these pores can serve as a way to seedc-Si overgrowth. We demonstrate that it is feasible to grow crystalline Si overlayers on top of such porous oxide barriers, while on the continuous Si-oxide surface, only amorphous or nanocrystalline Si layer overgrowth can be achieved. The controlled oxide growth and Si overgrowth on the oxide can find possible applications in Si-based resonant tunneling devices, optoelectronics, and other Si-based nanoelectronics. ©1997 American Institute of Physics.