The invention concerns a micro-machined vapor cell comprising a central silicon element forming a cavity containing vapor cell reactants such as alkali metal or alkali metal azide, buffer gas(es), and/or anti relaxation coating(s); a first and a second glass caps sealing the cavity; and a solenoid arranged to provide a homogeneous magnetic field to said vapor cell. The solenoid is coiled directly on the central silicon element of the vapor cell. This invention is an improvement for the highly miniaturized atomic clocks developments.