A low voltage high linearity MOSFET-only Delta-Sigma modulator for implantable neural signal sensors is presented in this paper. In order to reduce the capacitor area significantly, most of the capacitors in the modulator are implemented by the single PMOSFET MOSCAPs in inversion region. The rest capacitors are realized by series compensated MOSCAPs to ensure high linearity over the wide swing. A DC level shift technique is employed in the first integrator to guarantee the PMOSFET in the inversion region and thus extend the input signal swing. Besides, a 4-bit quantizer is applied to increase the signal-to-noise-and-distortion-rate (SNDR) and decrease the output swing of each integrator for the linearity optimization of MOSCAPs. The bottom terminal parasitic effect of PIP (poly-insulator-poly) capacitors is also eliminated completely as a result of MOSCAPs application. The modulator is simulated in a 0.35μm n-well standard CMOS process and achieves 104dB SNDR at 8k-Hz signal bandwidth. Compared with the PIP capacitor design, this work reduces about 77% of the total capacitor area.