We show that formation of oriented Si3N4 crystallites can be obtained by plasma nitriding of 20 nm thick SiO2 amorphous layer on Si (111) wafer. Nitriding is achieved at temperature in the range of 800–1000 °C with microwave plasma using gas mixture of N2 and H2. Results of x-ray diffraction and Raman spectroscopy show that both α-Si3N4 and β-Si3N4 are formed on the nitrided substrate and are strongly oriented in 11¯00 for both phases. The morphologies of the nitrided surfaces as shown by scanning electron microscopy exhibit elongated Si3N4 crystallites aligned with Si<110>. Cross-sectional transmission electron microscopy image reveals that the Si3N4/Si interface is sharp without residual SiO2.