A high-voltage monolithic active pixel sensor, designed to be compatible with standard deep sub-micron CMOS production lines, is described. The device can support a reverse bias voltage of −180 V and combines small collection electrodes with full wafer depletion, demonstrated up to a thickness of $300\ \mu \mathrm{m}$. Test structures consisting of matrices with an area of $2\ \mathrm{mm} \times 2\ \mathrm{mm}$ embedding 576 pixels with $50\ \mu \mathrm{m}$ pitch have been fabricated in a 110 nm CMOS process. The sensor concept is discussed and experimental measurements obtained on first prototypes are presented.