We present single mode quantum cascade lasers including a microscopic heater for spectral emission tuning. Through the use of a buried heater element, the active region temperature can be modified without changing the submount one. Emission frequency tuning in continuous-wave as large as 9 cm(-1) at 1270 cm(-1) and 14 cm(-1) at 2040 cm(-1) are observed, corresponding to an increase of the active region temperatures of ∼ 90 K. Due to the proximity of the heaters to the active region, emission can be modulated at several kHz range and the absence of moving parts guarantees the mechanical stability of the system. This method can be successfully applied to all buried heterostructure lasers, becoming an attractive solution for molecular spectroscopy in the IR. Using the presented devices, molecular absorptions of N(2)O have been measured between 1270 cm(-1) and 1280 cm(-1) and are in agreement with data from the HITRAN database.