Surface-oriented lateral mesa PIN diodes have been fabricated for the purpose of evaluating the feasibility of a silicon-on-insulator technology for microwave applications. For these devices, heavily doped p and n regions are formed from ion-implanted polysilicon diffusion sources which abut opposite sides of an intrinsic rectangular-shaped mesa, and electrical contact to the injecting contacts can be made with low parasitic series resistance. Devices for process evaluation were fabricated using a single-crystal silicon substrate (as opposed to recrystallized silicon-on-insulator films). Both d.c. and 3-GHz electrical characteristics indicate the desired conductivity modulation of the intrinsic region under forward bias. Moreover, the large breakdown voltage which is observed indicates that high peak-power handling capability should be possible.