This paper reports on the development of diamond probes integrated with an Si-based piezoresistive strain gauge for ultra-high-density ferroelectric data storage beyond 1 Tbit inch-2 with scanning nonlinear dielectric microscopy (SNDM). Only the tip of the probe was composed of diamond, and a cantilever integrated with the piezoresistive sensor was made of Si. The electrophoretic deposition process for diamond growth improved the production yield for sharp diamond tips. The radius of the tip was approximately 100 nm. Topographic imaging using AFM was demonstrated at a constant force mode to verify the performance of the fabricated probe with the piezoresistive strain gauge as a force sensor. The sensitivity of the piezoresistive strain gauge against displacement (ΔR/R) was about 1 × 10-7 nm -1. SNDM experiments on a LiTaO3 substrate were performed. Clear contrast of SNDM image was obtained using the diamond probe. Ferroelectric recording on the LiTaO3 film using the diamond probe was demonstrated. The obtained size of data bit was approximately 50 nm, which corresponds to the recording density of 250 Gbit inch-2.