We propose a novel acousto-optic (AO) devise using suspended fishbone nanobeams based on phononic and photonic potential well (PnPW and PtPW). We aim to reduce the traditional device size and eliminate the need for mirror regions in 1-D nanobeam cavity. By manipulating the frequencies of slow sound (SS) and slow light (SL) modes through geometric parameters, we can create potential wells for phonons and photons. The potential wells concentrate the waves inside the resonant cavity simultaneously, leading to an increase in AO coupling rate. We demonstrate the capability of potential wells in improving the AO coupling rate and investigate the impact of both wells. Some distribution of the phonons may affect the photons with a negative contribution, leading to a decrease in the coupling rate. Careful selection of appropriate acoustic and optical modes can overcome this limitation, making this structure a promising candidate for designing AO devices in silicon photonics.