A silicon-on-insulator wafer (10). The SOI wafer (10) comprises a top silicon layer (6), a silicon substrate (4), and an oxide insulator layer (2) disposed across the wafer (10) and between the silicon substrate (4) and the top silicon layer (6). The oxide insulator layer (2) has at least one of a contoured top surface (8a, 8b, 8c, 8d, 8e) and a contoured bottom surface (12e). Also provided are processes for manufacturing such a SOI wafer (10).