The invention provides a non-invasive skin treatment device (200) for generating a multiphoton ionization process at a target position (110) in skin tissue (102). The skin treatment device (200) comprises a laser source (105) configured and constructed for generating a laser beam (106), an optical system (109, 112) for focusing the laser beam into the target position below a skin surface (103), and a plasma unit (117) configured and constructed for generating a plasma (100) such that, in use, at least a portion of the plasma penetrates the skin tissue for generating at least one free electron at the target position. The skin treatment device further comprises a control unit (123) configured and constructed for controlling the laser source and the plasma unit such that, in use, at least a portion of the light of the laser beam is absorbed by said at least one free electron generated at the target position, thereby generating the multiphoton ionization process. A result of the use of the plasma in generating the multiphoton ionization process is that an overall laser beam intensity, required to generate the multiphoton ionization process, is reduced as compared to skin treatment devices which generate the multiphoton ionization process using a laser beam only.