A new monolithic thermal inkjet printhead using single crystalline silicon island as a heating resistor is proposed. The n(+) silicon island was fabricated by full isolation by porous oxidized silicon (FIPOS) using double diffusion. The heating resistor is thermally and electrically isolated from the silicon substrate by oxidizing the porous silicon; The fabricated thermal inkjet, printhead has a simple structure because high quality thermal oxide can be used as a passivation layer.